Many papers, subject matter cartography, and more particularly those concerning the methodology of Claudius Ptolemy1 now include the “de rigueur” utilisation of computer programmes, computer generated visualisations and the Star Burst Plots which endeavour to illustrate data comparisons. That this usage of the computer does not of itself appear to offer any additional information to the subject matter and is merely presentational, should perhaps give cause for reconsideration by those authors of its usage.
This paper is not a polemic against the use of computer generated data, which certainly has its place when appropriately used. It is in fact questioning the over complication caused by such usage when simple maps or diagram maps used as the prime research tool would actually explain more.
This paper illustrates by example that the use of simple maps, for that is in fact all that Claudius Ptolemy has bequeathed to us, a fuller understanding of “Geographia” can be simply gained.
WHAT IS THE MARTELOIO?
In the four subsections which follow the Marteloio will be discussed in the manner each of the authors dictated or indicated. They are basically a table of distances which are determined by triangles. These are the triangles of wind directions that are formed in a circle of 100 mile radius, when the 100 miles is the hypotenuse of the triangle. Thus a triangle having a hypotenuse of 100 miles and being formed from the first quarter wind, 11.25 degrees, the distance sailed, the adjacent side would be 98 miles, whilst the distance off course from the zero degree wind would be 20 miles.
Thus they were be tabulated as follows;
The figures when first viewed make little sense as there is a disparity b
between the pairs of distances; columns 1 & 2 are predicated upon the 100 miles distance discussed, but the second pair are predicated upon a 10 mile distance which enables the mariner to calculate an actual course distance sailed, say 65 miles by a substitution of the units given.
The confirmation of that is simply the 8th wind quarter or 90 degree change and is the maximum distance quoted, 100 or 10 miles.
But how did the Marteloio come into being. If the figures for the first two columns of distances are studied they are simply the approximation for the Sine or Cosine of the wind angle multiplied by the 100 mile radius measurement.
Thus we can rewrite the first part of the table;
The second part of the table is merely an approximation when reduced to the tenth part. That is 100 reduced to 10 miles. The actuality and approximations are fully discussed later.
Thus within the following texts, although detail explanation is again necessary and given, the basic concept is simple and manageable by a competent mathematician.
It must be borne in mind that the Sine table is basically an Indian idea which was copied by Arabic scholars and hence Europeans became aware of it. Whether the Marteloio is actually an Arabic or European invention is open to question, with little chance of a resolution. But, these four texts do give an indication of that knowledge.
RAMON LULL: SECTION 1
There are two texts by Ramon Lull which include navigational references that may be the precursor to the Marteloio table, or even just a poor description of a table or text which describes the Marteloio. Some researchers even consider they were written on a voyage.
ARBOR SCIENTIAE, Page 569 and 570; Of Geometrical Questions.
De Questionibus Geometrie.
Principia Geometriae quae sunt? Solutio. Vade ad rubricam ante-dictum. Quare geometricus ante lineam diametralem considerat, quam triangularem? Solutio. Figura circularis ita divisibilis non est in aequalibis partibus sicut figura triangularis. Quare Geometricus primo multiplcat duo ex uno, & quatuor ex duobus, & octo ex quatuor, quam tria ex uno & sex ex tribus, & duodecim ex sex? Solutio. Illas mensuras quae citius multiplicand numrerum, Geometricus primo considerat, cum ita sit, quod quantitas comtinua ante sit divisibilis in discretam per numerum dualem, quam ternalem. Idcirco Geometri dicunt, quod numrus dualis est ita multiplication suarum mensurarum in duplicado, sicut in arte arithmeticae unius in numerando unum post alium. Marinarii quomodo mesurat miliaria in mari? Solutio. Marinarii considerat quatuor vetos generals, videlicet vetu orietale, occidentale, meridionalem, & ventum septemtrionalem, similiter alios quatuor ventos qui ex primis exeunt, considerant, videlicet grec, exaloch, lebig, & maestre, & centum circulos considerant in quo venti angulos faciunt, diende considerant per ventu orientalem navem euntem centum miliaria a centro quot sunt miliaria usque ad ventum de exaloch,& miliaria duplicant usque ad ducenta miliaria, & cognoscunt quod miliaria sunt multiplicata. Quae sunt ducenta a vento oriental, usque ad ventum de exaloch per multiplicationem miliarium, quae sunt de termino centenario orientis usque ad terminum de exaloch. Et ad hoc instrumentum habent chartam, compassum, acum, & stellam maris.
The translation is as follows;
“Questions about Geometry; What are the principles of geometry? Solution- go to the above chapter. Why does geometry consider a diametric line before considering a triangular line? Solution- a circular figure does not divide into equal parts as readily as does a triangular figure. Why does the geometer first produce 2 from 1, then 4 from 2, then 8 from 4 before producing 3 from 1, 6 from 3 and 12 from 6? Solution- the geometer first considers the measures which multiply by numbers most readily given that continuous quantity divides into discrete quantity sooner by the number 2 than by the number 3. Consequently geometers say that the number 2 yields the multiplication of measurement by enumerating one thing after another.
How do mariners measure miles at sea? Mariners consider the 4 general winds, that is to say the eastern, Western, Southern and Northern, and also another 4 winds that lie between them, grec (NE), exaloch (SE) Lebig (SW) and maestre (NW). And they look carefully at the centre of the circle in which the winds meet at angles; they consider when a ship travels by the east Wind 100 miles from the centre, how many miles it would make on the South east (exaloch) wind; and for200 miles they double the number by multiplying and then they know how many miles there are from the end of each 100 miles in an easterly direction to the corresponding point in a south east direction. And for this they have this instrument, and a chart, compasses, needle and Pole star. (Or, to do this they have instruments such as maps, magnetic compass needle and astrolabes!)
In the second text of Ramon Lull, (1305), ARS MAGNA GENERLIS ET ULTIMA, taken from the 1517 printed edition are the following sections; pages 215-217, ‘De Navigatide’ and page 273, ‘De Questionibus Navigationis’. But as they are in Medieval Latin shorthand I have not included a copy of the text or retyped the original.
The translations are as follows;
Article 96; NAVIGATION
“Navigation is the art by which sailors know how to navigate the sea. Navigation is originally derived from geometry and arithmetic, through motion and its correlatives signified by the second species of rule C, namely the mover, the mobile and the act of moving; and through time and place, because a ship is in one place at one time and in another place at another time. Given that arithmetic and geometry are derived from this art – as we proved in previous articles – it is therefore clear that the art of Navigation originates in this art first of all, and is subsequently derived from geometry and arithmetic. To clarify this, we first draw this figure divided into four triangles, as shown, and consisting of right, acute and obtuse angles.
Supposing that the place where four angles meet is due north, and this is where the ship’s port is, shown by the letter B. From here, a ship wants to sail eastward, but is actually on a course due southeast, so that when it sails 4 miles, those 4 miles due southeast amount to 3 miles of progress eastward; and when the ship sails for 8 miles, this only amounts to 6 miles of eastward progress; and if it sailed 100 miles, it would amount to 75 miles eastward. And thus, the arithmetician calculates by saying that if 4 miles amount to 3, then twice 4 amounts to 6, and if 4 times 4 equal 16, the three times 3 equal 9, and so with other multiplications of this kind, in their different ways. The reason for this is that in motion, first there is a point, followed by a line, then followed by a triangle, and then by a square, by reason of which successive local motion is generated through multiplication. And this is signified by the previous articles on the point and the line. This kind of natural motion and multiplication is unknown to sailors and navigators, although they know what it is to experience it. And to shed further light on this experience, we will provide doctrine about it.
If a ship leaves the port B and wants to sail due east, but is actually on a southward course, it then deviates twice as much as it would if it sailed southeast. This is because southeast is between east and south. And if the ship is on a south westerly course while it wants to sail eastward, it deviates 3 times as much, and if it is on a westward course, it deviates 4 times as much. And here the intellect sees how the ship’s motion is composed of straight and oblique lines. We have shown a method with which sailors can gauge the deviation of their course from the intended destination, now we intend to provide a doctrine and art to enable sailors and navigators to know where a ship is located at sea, and we will show this by an example of calculating distances between different mountains.
Let L be a mountain 4 miles to the east of port B (where the ship is moored). M is another mountain 4 miles southeast from port B and N is a mountain 4 miles south of the port. Let O be another mountain 8 miles south of the port. Now we ask; how far is L from N and from M, and how far is O from L and M?
In answer to the first and second questions, we say that sailors can gauge these distances by multiplying the miles and calculating the deviation. Now if 4 miles amounts to 3 it follows that mountain L in the east is 3 miles from mountain M in the southeast, and 6 miles from mountain N in the south. And if mountain O in the south is 8 miles from the ship, then the sailor reckons that O is proportionately more than twice as far from L as it is from M in the southeast.
In answer to the third question we say that there are 8 miles from port to O, and four miles from L to the port, which shows that L is 9 miles from O.
In answer to the fourth question we say that O is 8 miles from the port, and M is four miles from the port, so that M is 6 miles from O. And this is the solution to the 4th question.
Following the example in which the distances in miles between mountains L, M, N and O were reckoned, this art can be applied by the artist for proportionally reckoning the distances in miles between other mountains, by multiplying miles in triangles and squares; because just as the arithmetician multiplies numbers by calculating that 3 times 3 equals 9 and 4 times 4 equals sixteen, so can the sailor also make his calculations. Thus we have clarified a method by which sailors can determine the position of a ship at sea, by gauging the distances from north and east, south, as well as west, southeast, southwest, northwest and northeast, with respect to the ship’s position. And this doctrine is easy, brief and most useful; it is general and applicable to particulars.
By rule G and by the subject of the elementative we know that if a wind blows from the east, it is more inclined to the southeast than to the northeast, because the southeast is moist and warm, whereas the northeast is cold and moist, since it is caused by the north. And if the wind blows from the southeast, it is more inclined toward the east than toward the south, because the south is hot and dry. And the same can be said of other winds in their different ways.
Then the sailor must consider different qualities of air; cold, gross air heralds the north wind; moist and tenuous air heralds the east wind; warm and subtle air heralds the south wind; dry and cold air heralds the west wind.
The clouds signify the winds by their colours; red clouds herald the east wind; golden clouds herald the south wind; white clouds herald the north wind; black clouds herald the west wind. Clouds composed of several colours herald a mixture of winds, and the prevalence of different colours signifies the prevalence of the winds they stand for.
Rain coming from a direction signifies wind from the same direction. And the same applies to lightning and thunder in their way. A whirlwind at sea signifies wind in circular motion taking on a shape like a snail or conch shell, by whirling around in a circle to raise seawater aloft as if it were fine dust rising from the ground. And a whirlwind’s colours signify different winds in the same way a cloud’s colours do.
We need not deal with magnets and iron in this article on Navigation, because what we know about them from experience is sufficient. Here we need not seek to know why a magnet attracts iron, as this topic does not belong here, but with the natural sciences. Those interested in the natural sciences can look into this for themselves. And the intellect is delighted to reflect on the things said here about navigation, because it has been amply instructed about the art of Navigation.”
The translations of the Medieval Latin text used by Ramon Lull may be found at, http://lulliquarts.net/cont.htm
Diagram ChMa1D01 – The text of Ramon Lull is simply illustrated by two diagrams (or one combined) indicating that his approximation of the South East wind being at a ratio of 3:4 from the East wind is slightly inaccurate; i.e. 45 degrees becomes 41.41 degrees. In terms of medieval sailing in the Mediterranean Sea, coasting mainly, this deviation over short distances would be quite manageable, actually capable of being ignored and thus a reasonable rule of thumb. When it becomes 100/75 miles however, the deviation is still only 4 miles from the 45 degree course and hardly noticeable with the inaccurate compasses and charts of the day.
Thus it is quite possible to opine that Ramon Lull may have learnt this rule of thumb from a mariner, or simply applied his mathematical skills to the simple problem.
A CURIOSITY; TEXT OR DIAGRAM
However, between Ramon Lull’s 1295 and 1315 texts and the next section there is the distinct possibility that another text or texts and diagrams were available for both Michael of Rhodes (1434) and Andreas Biancho (1436) to draw upon. In 1390 the inventory of the mother of Oberto Foglieto of Genoa an entry reads; “unum martelogium—item carta una pro navegando”. (see Albertis, E A.  page 118). Thus provenance of origin is difficult.
MICHAEL OF RHODES, VENETIAN MARINER: SECTION
In 1434 Venetian mariner Michael of Rhodes (Michalli da Ruodo) had risen through the ranks of shipboard life and was preparing himself for the interview or examination which would elevate him to the highest position in the Venetian fleet a commoner could hold; that of ‘Homo de Conseio & Armiraio’. He attained and held that rank, 1435-1443.
Whether it was to aid his elevation or not, Michael of Rhodes at this time started to write a personal manuscript which by the time it was completed in the 1440’s was to cover mathematics, navigation, astronomy, astrology and even ship-building techniques. It was as stated a personal document, just one copy, and included a record of his voyages and other information obtained during his travels.
He wrote a second manuscript into which he copied some of his original text information concerning sailing techniques etc., amplifying some of the sailing direction information, but this text is considered as being usurped by Pietro di Versi, who added his name to the text entitled; “Raxon de Marineri”, Taccuino Nautico del XV Secolo (and now published in Venice edited by Annalisa Conterio). The original manuscript is held in the “Biblioteca Nazionale Marciana, Venice, as Ms It., cl., IX., 170 (=5379).
The original of Michael’s text was lost for centuries and when it resurfaced was made available via the ‘Dibner Institute for the History of Science and Technology’.
Therefore, being a personal document we must accept that it is written without long explanations, the author knew the texts, and thus much of the preparatory information on our subject is missing. This text concentrates upon four pages, 47a, 47b, 48a and 48b which discuss navigation and the Marteloio and are thus linked to the work of Ramon Lull which preceded this section and also the work of Andreas Biancho and ??, which follows.
MICHAEL OF RHODES; NAVIGATION; THE METHOD OF MARTELOIO
Within the four pages M of R endeavours to explain a mathematical solution to sailing discrepancies and their correction to attain an intended course or destination. As this is a private document, which may have been written with future publication in mind, it is perhaps neither self-explanatory nor adequately filled with examples which he would have made use of in his career. As will be readily observed they are quite superficial examples of sailing problems.
M of R commences his text with;”This method called the ‘Marteloio’ for navigating mentally, as I set forth systematically below”.
This does not mean that the solution to a mis-direction can be ascertained just by thinking about it, (although as will be shown in some instances by a simple thought it could be solved), but, that you must use your mental faculties, a knowledge of simple mathematics, multiplication and division, to solve the mis-directions in sailing.
He continues;” First is the distance off course; second is the advance; third is the return; fourth the advance on the return, and each of these has 8 daughters. And first;
The distance off course 8, that is; 20, 38, 55, 71, 83, 92, 98, 100.(called the alargar)
The advance 8, that is; 98, 92, 83, 71, 55, 38, 20, 0
The return 8, that is; 51, 26, 18, 14, 12, 11, 10.2, 10
The advance on the return 8, that is; 50, 24, 15, 10, 6.5, 4, 2.2, 0
Thus he has set down a table of distances which can be used to determine the result of mis-direction once the regime has been understood as there is no explanatory text. The tables give a clue to the distance measures used to regulate the mathematics; distance off course and advance are predicated on a distance of 100 miles; return and advance on return are predicated on a distance of 10 miles and are thus subject to rectification if they are used for distances up to 100 miles.
The table is listed in such a way that it does not aid natural usage. Firstly, each of the ‘daughters’ must be recognised as the quarter winds of a quadrant; 11.25, 22.50, 33.75, 45, 56.25, 67.5, 78.75 and 90 degrees, and they are listed in that order such that the distance off course of 20 miles, that is 11.25 degrees or 1 quarter would mean that on the original course line the ship would have sailed 98 miles.
It would appear Michael of Rhodes recognised this problem of identification for at the end of his text he sets down the table using the quarter terminology. Thus we can insert that table here to aid the discussion.
TABLE OF MARTELOIO
His text continues;
“And for an example of this rule, let us say that a land is 100 miles to the east of you, how much do I want to go east southeast, which is 2 quarters so that the land will be north by east of me, which is 7 quarters, and how far would I be from that place? And below is written the way according to this technique”. Diagram ChMa1D03
Note well that it is a simple triangle and the winds chosen naturally form the precise opposite wind and thus the return should be simply noted as 100 miles. Thus if it is a simple triangle by drawing a horizontal line east/west and mark off 100 miles; from the west draw a line east southeast, that is 2 quarters or 22.5 degrees and from the east draw a line on the opposite course, actually north by east projected south by west and they will cross naturally, indicating the outward and return courses and distances. What will be noted from this diagram triangle is that both the intended distance and the distance sailed ESE are one and the same. But it is never stated and is therefore a questionable fact of knowledge. Can we prove that fact?
His text then continues;
“Take the distance off course that you want to remain, which is 7 quarters, which is 98/10, then we will add the 2 quarters that you go and the 7 that you seek which will be 9 (quarters). So here is the return of 9 quarters, which is 10.2. We multiply and we say in this way 98/10, 51/5, and multiplied together, multiplied and divided is 99 48/50 miles.
And we will be that far wide of the place”.
At this juncture it is worth noting that to achieve the figure for 9 quarters it is necessary to count forward 8 and back one quarter, and thus any number over 8 is achieved. The text requires that the table be used to provide the distance measures to calculate the ESE end point position, and he calculates that the ship will be 99 48/50 miles ESE of the start point. That is obviously the 100 miles equivalent of the actual voyage, but not stated!
Here it is worth inserting the corrections to Michael of Rhodes table, as it is an approximation of the true distances. The whole table is predicated upon 100 miles and then 10 miles and is no more than an extrapolation of the cosine ratio’s for the quarter winds;
1st quarter = 100 Cos 11.25 = 98.0785, with 98 actually used. Little error
2nd quarter = 100 Cos 22.5 = 92.388, with 92 actually used. Large error
3rd quarter = 100 Cos 33.75 = 83.147, with 83 actually used. Medium error
4th quarter = 100 Cos 45 = 70.71, with 71 actually used. Little error
5th quarter = 100 Cos 56.25 = 55.56, with 55 actually used. Large error
6th quarter = 100 Cos 67.5 = 38.268, with 38 actually used. Large error
7th quarter = 100 Cos 78.75 = 19.51, with 20 actually used. Large error
Hence it is obvious discrepancies will inevitably arise, and errors accumulate.
Next we read,
“Then we want to say how many miles we will be away from that place. And wanting to make this calculation, do the opposite of what you have done and say that the distance off course of 2 quarters is 38/10 and the return of 9 quarters is 10.2, and multiply 38/10 times 51/5, multiply and divide, will make 38 38/50 miles. And so we will do all calculations similarly.”
Thus we now have the full triangle sides with their measurements such that the original west/east is 100 miles, the ESE is 99.96 miles and the NbE is 38.76 miles according to Michael’s figures.
But what he has given as an example is perhaps for ease of mathematics using virtually the same figures (i.e. only 98 becomes 38) and thus is perhaps a spurious example because it indicates the ship sailed c139 miles to cover an original 100 miles; that is too much extra as time at sea which was unnecessary would be costly to merchants.
A simple diagram of triangles will indicate that the voyage could be as little as c104 miles and up to c139 miles. Thus by illustrating the simplest method using the 100 mile distance he has suggested an extraordinarily excessive sailing distance. Did he understand the figures?
The next example given in the text is;
“And if you want to tack, that is turn, to know how to return to the course and see the advance you have made, it is done in the same way as the advance, as you will see systematically below. And for example, my course is to the east and I cannot go, and we go 100 SEbS. How many miles do I want to go NEbE so that I come to my course, and how much will I have advanced?
This is the method which is the distance off course of 5 quarters which is 83/10 and the return of 3 quarters which is 18. Multiply 83/10 by 18/1 makes 1494 and divide by 10 will be 149 4/10ths miles and this many miles we want to travel to our course.
And if someone asks you how much we will have advanced here is the way. Take the advance on return of 3 quarters, which is 15, and the distance off course of 5 quarters that is 83/10, multiplied and divided will be 124 5/1oths and then add the advance on the distance off course of 5 quarters which is 55, added makes 179 5/10th miles. You have advanced that much.”
Again by simply using the 100 mile distance sailed the figures are a direct abstraction from the table and the angles chosen, SEbS to NEbE is merely a 90 degree course change which would have produced the simplest reckoning for a mariner. That is 100 divided by Cos 56.25, the 3rd quarter equals 55.557/100 and thus it is 100 x 100 divided by 55.557 = 179.99 or actually 180 miles total advance. Then 179.99 x Cos 33.75 or 179.99 x 83.147/100 = 149.656. Thus in round figures, sail 100 miles SEbS, turn 90 degrees to sail NEbE for 150 miles to your original easterly course and you will have advanced a total of 180 miles.
By not noticing or deliberately avoiding the simplest triangular calculation when the whole Marteloio is predicated on triangles having a 100 mile measurement, the example is oversimplified and requires angles and distances of a less simple nature to fully explain the obvious capabilities of the Marteloio.
The next example is perhaps the corollary to that statement. He continues;
“And by another calculation, my course is to the west and I cannot go, and we go 100 miles WbS. The wind goes on and we go toward WSW, 100 miles. The wind goes on and we go SWbW 100 miles. The wind goes on and we go SW 100 miles. I ask how many miles I want to go NW so I come to my course and this is the way and how much I will have advanced.
And we will say that the distance off course of 1 quarter will be 20, and of 2 quarters, 38, and of 3 quarters, 55, and of 4 quarters 71. Added all together it will be 184. And then we will say that the return of 4 quarters is 14. Multiply 184/10 with 14/1 makes 2576 divided by 10 makes 257 6/10ths miles. And that is how many miles you will have travelled to get to the course.
And what will I have advanced on the return of 4 quarters? It is 10 multiplied by 184/10 makes 1840 divided by 10 will be 184 miles. And then we will say, what is the advance on the distance off course? From 1 quarter it is 98 and 2 quarters 92, and 3 quarters 83, and 4 quarters 71. Added together make 344 added to 184 makes 528. And this much you will have advanced”.
Basically little mathematics is required in this example, merely additions and recognising that again the angle of return is 90 degrees to the penultimate course. This is in fact what Michael of Rhodes has stated and must have been aware of as he has said the penultimate course is SW and the return is NW, a 90 degree course change. Thus by adding the advances, 98+92+83+71=344 advance and then the alargars, 20+38+55+71 = 184 alargar, because the return is 90 degrees the alargar must equal the second portion of the advance and give the total of 344 + 184 = 528 miles advance. The return is thus simply 184 x 100/71 = 259 11/71 (259.156 or 184/Cos45).
His final section of the text is altogether a different calculation, one fraught with mis-description leaving too many assumptions and translations to be made. In fact it appears to be an unconsidered addition as the original paragraph first words have been erased.
Having read the text many times to understand its mathematics and in fact comprehend just what he is actually stating has led to the conclusion that it was written whilst studying a diagram and thus each separate section must be carefully analysed sentence by sentence to separate the sections properly and understand the whole.
Here is the complete text, which will be subdivided for ease of explanation;
“And if someone asks you; [what will I have]. Another calculation, a land is west of me in the evening and I cannot say how many miles we go in the night. In the night we go NW 41 8/10ths miles and in the morning that land is towards the WSW”.
It must be evident here that M of R is copying or not concentrating on his text.
“How many miles is the distance now that the land is towards WSW, and how many miles was it in the evening when it was to my west? You should do it this way and say that my distance off course for 2 quarters 38/10 and the return of 6 quarters is 11. Therefore multiply 38 x 11 making 418, divide by 10 will be 41 8/10 miles you will have travelled.”
At this juncture it is so very apparent that there has been a methodology fiddle; or he is reading from a diagram. Why start by stating the distance and then prove it.
But he continues;
“And how far away will you be when it stands WSW of which the distance off course 4 quarters is 71/10 and the return of 6 quarters is 11? Multiply 71/10 by 11/1 makes 781, divide by 10 it will be 78 1/10 miles. You will be that far away.”
Having copied out both sections it now becomes apparent that he has miscopied from a diagram or from notes for the text. If a diagram is studied that sets out both examples then it will be seen that the distance of 78 1/10th miles is in fact the resultant of the 4 quarters when the distance travelled off course is 41 8/10th miles. If the return distance is noted for the first or 2 quarter diagram it is 41.131, which could be 41 8/10th miles by his figures. With the 2 quarter diagram the original distance is 92 miles plus 15.74 miles and for the 4 quarter diagram it is the 100 mile base figure. It would therefore appear that Michael of Rhodes has inadvertently mixed the 2 and 4 quarter figures for his solution. But it is not the end point.
He finishes thus;
“And to know how far away you were yesterday when it stood to the west, go back the opposite of your course and go SE that which remains to the west, such that it stands WSW you will go 53 1/5th miles. Reduce by a quarter and 39 2/10 or 39 9/10th miles remains and you will be 126 4/5th miles away. Reduce by a quarter there remains 96 2/5th miles. And you were that far away in the evening.”
This is no doubt a complete misreading of a diagram or misunderstanding of another person’s text. The only point which will allow a reverse voyage of 53.2 miles to attain a WSW position is the apex of the 4 quarter triangle. But the actual WSW position is 58.2 miles from that apex, thus giving a total side of 100 miles from 58.2 + 41.8 = 100 miles the hypotenuse distance of a 71 side triangle.
The distance 126 4/5th miles is only valid from a diagram and not a calculation, but the 96 2/5th miles distance can be assessed via a simple 2 quarter angle against the 1 quarter off course 20 mile distance as the diagram illustrates.
To understand the last section a Tondo e Quadro was constructed, called LINES.
LINES; JUST HOW MANY CAN BE DRAWN?
If we study Portolan Charts, one obvious comment is that they are covered in angled lines, wind direction lines and it appears there are virtually as many as it is possible to draw. If only the necessary lines were drawn it would be just the 32 quarter wind lines projected from a single point across the face of the chart. But every conceivable wind is drawn as many times as it is possible until the cartographer has filled the chart and in fact made it harder to read.
If we reread what Michael of Rhodes has written in the final paragraphs it can be seen that they are totally outwith the first basic premise calculations.
Thus if we construct a diagram of the Marteloio, rather than a table format as is normal we can evaluate any description made of a voyage by wind direction.
Basically we have a single quadrant of winds, that is 8 sections of 11.25 degrees, but if we draw the quadrant not as a quarter circle but as a square there can then be drawn a multitude of lines in 3 or 4 directions. Thus it is possible that a diagram of the Marteloio was used to write the text and not the tables that appear at the beginning and end of the 4 pages of his text. The number of lines is reminiscent of the Portolan chart and when the winds are drawn from both east and west terminals they indicate half quarter wind positions also. Thus the strange distance of 126 4/5th miles can be explained.
CURIOUSITIES WITHIN THE TEXT
|Obviously in the first section Michael of Rhodes has written one fact and immediately contradicted it with the distance of 41.8 miles. But even more important is the fact that he knows the Port he wishes to attain after sailing that distance is WSW.
Michael of Rhodes was a mariner and therefore must have understood the distance it is possible to see from the masthead of a ship. The horizon from a masthead of say 13m is only 8 miles away and even if the land was 13m above sea level it would only increase to 16 miles visual distance horizon. Thus we can only surmise that the whole text is based upon the Marteloio tables, it is a fiction predicated upon 100 miles distance and is not therefore a text written by someone who comprehended the system but by a person who stumbled across the idea and thought he knew how to use it.
The text is therefore a fiction written on the spur of the moment, copying the work of others and being basically misunderstood. Either that or Michael of Rhodes actually had little or no mathematical knowledge with which to fully appreciate what was being stated by the original author and did not understand the simple triangle and its properties.
COMMENTS AND TEXT BY OTHER RESEARCHERS
In a text regarding Michael of Rhodes, Professor Raffaella Franci makes the following points; I quote;” firstly that Michael’s treatment begins with the presentation of the table, and its method of use is explained by solving three problems. In contrast to his usual practice, the author neglects to transcribe the calculations for the arithmetic operations involved. Instead these calculations are found in the solution of the Martoloio problems that Michael presents in “Raxon de’ marineri”, another text which is attributed to him which we shall speak about more extensively below. In this second treatment the author solves six problems, the first three of which match those that appear in our manuscript”
“Among the nautical notebooks, the examples most frequently cited by scholars are those attributed to Cristoforo Soligo50, Zorzi Trombetta51 and Pietro Versi. The last of these was published in 1991 by Annalisa Conterio who noted significant similarities between the two, just on the basis of the Michael of Rhodes manuscript description in the Sotheby’s catalogue52. Franco Rossi has recently demonstrated that the manuscript attributed to Versi is actually the work of Michael of Rhodes. He has also verified that the direct comparison of the two texts reveals a virtually total correspondence between the first text and the second part of our manuscript53. In fact, mathematics is missing from the ‘Raxio de’ marineri’; only the ‘ragioni del martoloio’ appears. Nevertheless, we note that mathematics is also virtually absent in the other two notebooks mentioned above.”
“From the outset we have underscored the ample space that Michael devotes to mathematics. Reading the text then made us aware that much of what he writes has nothing to do with his actual professional demands. This theory is also bolstered by the fact that other nautical notebooks known today, including ‘Le raxion de’ marineri’ which he himself compiled and which has reached us under Pietro Versi’s signature, almost completely ignore mathematics. Furthermore, these same commercial notebooks often include mathematics as a smaller proportion of the whole. Why did Michael devote so much space to this subject, including long theoretical sections? To this question we can only respond with some hypotheses.”
“One answer could be in part related to another question; why did Michael write his notebook? Historians tend to answer this last question with the compilers’ need to have available the elements applied in their business activities. Yet this answer does not seem entirely valid in our case; in fact by his own account Michael took on the compilation of the text in 1434, when a good 33 years had passed since he first started out as an oarsman on a Venetian galley in 1401. Since then he had made a career and had become first an officer and then a captain as well, undoubtedly thanks also to his technical knowledge accumulated over the course of the years and which he now wrote up in his notebook. So perhaps it had been compiled to be exhibited as evidence of his qualifications, in order for him to obtain a post in public administration upon completing his service at sea. To this end, demonstrating a good understanding of mathematics was perhaps just as (if not more) important than demonstrating competence in the other subjects contained in the text. Naturally, this is only a hypothesis; however, based on the last annotation placed at the end of the autobiography (also repeated in folio 204), we do know that in 1444 Michael secured the public appointment of ‘officer of the steelyard’ (ufficiale della bilancia)57.” End of quotes.
Thus the text we have analysed by Michael of Rhodes is no doubt a preparatory text with regard to the Marteloio and its usage, but it shows an inconsistency of thought and usage and a complete lack of knowledge regarding the simple facts concerning triangles.
SECTION 3, ANDREAS BIANCHO
ANDREAS BIANCHO DE VENECIIS ME FECIT M.CCCC.XXX.vj
RAXON DE MARTELOIO: SAILING DIRECTIONS IN 1436 AD.
In 1436 Andreas Biancho published “Atlante Nautico”, an atlas of marine charts for the general area of the Mediterranean Sea and Black Sea. It encompassed the western sea-bord of Europe and Africa from the Baltic Sea to Cape Bojador and eastwards to Georgia.
Andreas Biancho included a single sheet entitled ‘Raxon De Marteloio’, which is a computation and drawing method for correcting the course of a ship when adverse winds affect its progress. It is based upon the 32 winds of the compass rose for calculations, (although he only illustrates the South East Quadrant), and informs a captain of his distance off-course and the true distance and return course to use in order to sail again on the original intended course.
Examples have been given in other texts of the use of the ‘Raxon de Marteloio’, but none appear to have produced what is, from Andreas Biancho’s own calculations the simplistic system he has designed. This text sets down that system, illustrates the missing research and indicates the origination of the idea and the reasons for the errors within.
As Diagram ChMa1D10 illustrates, this first sheet within ‘Atlante Nautico’ contains a descriptive text, three tables for calculations, the ‘Toleta de Marteloio’ which includes that which Andreas Biancho names the “Tondo e Quadro”; a semicircle with 16 winds; a circle with 16 winds plus alternates from the East and NbE nodes and a wonderfully drawn wind rose with the eight major winds noted, namely, Ostro (south), Libeccio (sw), Ponente (w), Maestro (nw), Tramontana (n), Greco (ne), Levante (e) and Scirocco, south east. The north point, Tramontana, is emphasized although it is drawn (perhaps) upside down.
The text there-on explains in somewhat strange and idiosyncratic medieval terms the ideology of the ‘Raxon de Marteloio’, and is as follows, with a translation.
“questo si xe lo amaistramento de navegar per la raxon de Marteloio como apar / per questo tondo e quadro e per la toleta per la qual podema saver chose chomo xe / la toleta a mente e daver andar per ogna parte del mondo senca mexura / e senca sesto choncosia che alguna per son ache vora far questa raxon eli a luogo / a saver ben moltiplichar chen partir Amaistramento del mar sie per saver / ben navegar e si se vuol saver la suma de marteloio per questo muodo quanto / se avanca per una quarta de vento e quanto se alarga chosi per una quarta e per / do e per tre e per quarto e se algun te domandase per queste sume se pol far tute raxon de navegar con cosia che nui non podemo saver la raxon chosi a ponto / ma nui se achosteremo ben a la veritade Anchor ate voio mostrar per cotal / muodo foxe una nave che vol andar per ponente e non de puol andar e si va / una quarta una de soto in ver el garbin mia cento a alargase mia vinti dal po / nente e avanca nonanta oto e per do quarte se alarga mia trena oto e avan / ca mia nonanta do per tre quarte se alarga mia cinquanta cinque e avanca / mia otantatre per quarto quarte se alarga mia setantaun e avanca mia / setantaun per cinque quarte alargo mia otantatre e avanco mia cinquanta / cinque per sie quarte se alarga mia nonantado e avanco mia trenta otto / per sete quarte alargo mia nonan ta oto e avanco mia vinti per oto quarte alargo mia cento e avanco mia nesun impero se lo retorno lo qual xe schroto in la toleta de Marteloio chomo apar per le suo chaxelle a le ssuo righe.”
That translates as follows;
“This is the way to learn how to sail, through the system of ‘martelojo’, made of this circle, this square and this table, which helps us to know things that we can easily remember by heart, so that we can go around the world without ruler and dividers. From the sea you will learn how to sail properly. A person wanting to use this system needs only to be able to multiply and divide. And one can know the sum of ’martelojo’ in this way, how much you go forward with a quarter of wind, and how much you go offshore: and similarly for one quarter, two quarters, three quarters and four quarters.
And, if one wants to know, through this system you can understand all the courses for sailing. Although we cannot know perfectly the course, we will be very close to the truth.”
Thus we can understand that Andreas Biancho intended this to be the simplest of systems, capable of being used by mental arithmetic and thus uncomplicated as the following text explains.
THE THREE TABLES EXPLAINED
The primary table set out adjacent to his text has within it the measurements from the text, but set to a circle of 100 unit radius, which the quarter winds, 11.25; 22.5; 33.75; 45; 56.25; 67.5; 78.15 and 90 degrees in a quadrant would subtend if projected onto a square encompassing the circle. That is the 11.25 degree wind “una quarte” line at the circumference is 98 units from the centre and 20 units from the horizontal line. There is a repetition of the units in reverse order after the 45 degree or centre line of the quadrant as is to be expected.
The two larger tables are in fact one and the same with the second correcting scribal errors in the first, which tends to suggest a modicum of copying. These two tables have a single notation which aids the unraveling of the second set of figures in each. That is “de ritor:10”, and this signifies that the figures set below this heading refer to a distance of 10 units and not the 100 units of the circle.
A question arises, that if the two tables are one and the same with the second slightly more accurate, and as it appears to be hurriedly written under the “Tondo e Quadro”, is it in fact just a correction for the framed table, the tabulated figures, which were realized as wrongly copied? And, secondly what were they copied from?
However, the system promulgated by Andreas Biancho becomes curiouser when the third and last table is studied. This table represents the figures obtained from the quarter winds if the “di ritor” is only 1 unit and not the 10 units previously noted. Thus we should expect the ‘Avancar/Avanco’ to be simply the tenth part of the first (or second) table. This does not happen, but at least the division of 55 by 10, written as 5 1/12th could be explained as a scribal error for 5 ½. However, the tenth part of 92 is 9 1/5th, not 9 1/13th, which, although gives wind directions close to 22.5 degrees i.e. 22.716, is less accurate than the 9 1/5th which gives 22.44 degrees.
It is as if the tables had been previously written out and now mis-copied, but written by another person, as the errors are so very simple to read and correct.
But, as the calculations upon Diagram ChMa1D11 indicate the figures are accurate enough to form triangles with the third side always 10 units long, and thus the return journey to the original East course is always 100 units along a designated new wind direction.
It is therefore possible to opine that the whole ‘Raxon de Marteloio’ is predicated upon the distance to be sailed, “de ritorno” being identical to the outward distance and thus all that is actually being stated is “hand” the triangle you have sailed and return to course. In simple terms, sail the opposing quadrant matching quarter wind for the same distance, i.e. sail ESE out, but ENE ‘de ritorno’.
THE TOLETA DE MARTELOIO
Having established from the mathematics of the tabulated distances that the return course is none other than the precise opposite handed course it can be shown as the diagrams illustrate, to be correct using the distances quoted by Andreas Biancho.
The tables are simple distance measures based upon 100 miles, but, if the distance sailed is variable, new units are required to be calculated. (That is not entirely correct as the scale diagrams at 100 miles can just be altered by denoting them as a different length).
Upon the diagram the new distance chosen is 65 miles and it has been tabulated to indicate the change in the ‘Avancar’ distances.
ALTERNATIVE SAILING DIRECTIONS
The example given by Andreas Biancho is based upon an original intended course of Due East. Thus if a ship is blown off course by any of the quarter winds in the quadrant the return can be simply calculated. But, if the intended course was other than Due East then by diagram the correct return course can be established; i.e. intended was SEbE, actual SEbS and return is therefore EbS.
RAXON DE MARTELOIO
The “Tondo e Quadro” has been reconstructed and the angular disposition of the ‘rayons’ calculated. A quarter wind is 11.25 degrees and thus a half would be 5.625 degrees. To achieve that the spread would be 78.75 degrees and the “tondo e quadro” would therefore be a perfect square in a circle of 100 units and its size thus 2 x 70.71 or 141.42.
By drawing the square less than the circle the ‘rayons’ are compromised.
Curiously though the note in the circle states “Suma de questo quadro m la 160” or the sum of the squares is 160 miles. This comes from the text adjacent to the scale bar, “da una quarta alaltr.a xi mia 20 —-inti”, and would appear to translate as each square represents 20 miles and thus the total is 8 x 20 or 160 miles.
The second section of the diagram tabulates the possibilities using the “tondo e quadro” to return to your original course by a shorter sailing distance than the outward course and as prescribed by the original tables shown on Diagram ChMa1D12
CONCLUSION; SECTION 3
|Andreas Biancho in setting down the’ Tavola’ upon his diagram, “Raxon de Marteloio”, has allowed mariners via the “tondo e quadro” to plot their intended course, and then the actual course sailed and thus calculate and or draw there-on their return to the desired course knowing the distances to be sailed.|
But, in so doing, from the example chosen of a Due East course and deviations there-of, he has inadvertently produced a table which if plotted out describes no more than a simple written answer would give;” incident course out, reflected course back, with equal sailing distances”. That is, one quarter wind south requires a return of one quarter wind north with the same distance to be sailed and the ‘Alargar’ or distance from the original course is an unnecessary unit of measure.
It is only when the return leg to the original course is not to be the precise opposite that is a total of double the distance to be sailed, that the tables become of great use.
Hence a simple “Tondo e Quadro” with the squares being denoted by whatever distance measure the mariner required would have sufficed, as Diagram ChMa1D16 illustrates.
If the “Tondo e Quadro” had not been drawn in the circle then its usage for the four quadrants would have been quite perfect as it could be turned if necessary.
But it is an example of new knowledge, mathematics again being of use to ordinary persons, but the implications of the mathematics in this instance are not realized by the author or originator of the system we have just discussed.
ANDREAS BIANCHO, ATLANTE NAUTICO 1436;
Andreas Biancho de veneciis me fecit M cccc xxx vj. A cura di Piero Falchetta, 1993, Arsenale Editrice srl, Venezia, Editione special per il Banco San Marco. Del presente volume sono stati stampati 1500 esemplari numerate. Questa copia portail numero 1148.
There is a complete web page at http://en.wikipedia.org/wiki/Rule of_Marteloio
but the text is incorrect and the explanations have been partially rewritten to explain the ideas of Andreas Biancho correctly. It is written in terms of 20th century mathematics and is over complicated with mathematical formulae that are unnecessary. More revision is required!
UNKNOWN AUTHORS TEXT; Section 4
Found by Professor Raffaella Franchi and included in her text as follows;
Astronomia/Astrologia In Un Trattato D’Abaco Della Prima Meta Del Quattrocento.
(Ms. Magl. Cl. XI, 119, della Biblioteca Nazionale di Firenze)
Folio numbers; c.202v, c.203r, c.203v, c.204r, c.204v, c.205r, c.205v, c.206r, c.207v, c.208r.
Abstract by Professor Raffaella Franci;
The paper presents the transcription of the chapters devoted to astronomy/astrology in the Abbacus treatise contained in the manuscript, Magl. Cl. XI,119, written in the first half of the 15th century. The treatment of this subject in the manuscript differs in many interesting aspects from that in the others so far studied. Among the subjects represented we find; tables to find month to month the day and hour of the moonrise; a method to calculate the initial day of the month; a rule to build a sundial; lunar prognostica and a table for sailing (tavoletta da navigare). The presence of the last subject is very interesting, its presence in abacus treatises is in fact very unusual.
A word of explanation regarding the winds etc., and the translation. Ruota Stellata=sailing steering wheel (da timone) chart; Ponente=west wind, westerly and west; Magistro or Maestro is the northwest wind; Dove E questo segnale= where is this position; Tramontana= north wind; Avanzare= sailing forward; Allargarsi= sailing wide and crocie, cross means 90 degrees. The winds are as follows;
Ragione della tavoletta da Navchare come vedi nella Routa stellata
Meaning of the sailing steering wheel chart that you can see in the graphic below.
Questa e la ragione della tavoletta sommata da navicare et diremo: se tu debbi andare per uno vento et non vi puoi andare et vai una quarta o due quarte o 3 quarte o uno vento intero o 5 quarte o piu o meno che dicessi. Verbi gratia noi dobbiamo andare per ponente et non vi possiamo andare et andiamo meno di ponente una quarta di vento verso lo magistro dove e questo segnale…., (1) I dico ch’avanzi per diecina Miglia 10 meno 1/5, che ai perduto di tuo viaggio 1/5 di miglio e sse’allargato Miglia 2 per decimal; cioe quandro sarai andato Miglia 10 per quarta meno di ponente Miglia 2, dunque quandro sara’ andato 100 miglia per quarta meno di ponente, saro alargato 20 miglia, poiche ssono 2 per decina.
This is the explanation of the graphic table of the sailing steering wheel to be used to sail and we say: if you have to sail along a specific wind, but it is not possible, you (would be forced to) sail a quarter or two quarters or three quarters of a wind, or a complete wind or 5 quarters (of a wind) whatever the case. For example, we have to sail towards Ponente (west), but we cannot, we sail instead a quarter less of a wind towards Magistro, where this sign is…, (1). I say that you sail 1/5 less 10 miles forward each 10 miles, because you have wasted 1/5 of a mile in respect to your journey, and (at the same time) you have sailed 2 miles wide each 10 miles; that is when you have sailed for 10 miles forward a quarter less Ponente 2 miles, then when you have reached 100 miles forward, a quarter less Ponente, you will have sailed 20 miles wide, as it is 2 miles (wide) each ten. Diagram ChMa1D07
Dei andare per ponente et non vi puoi andare et vai meno due quarte di ponente, cioe intra ponente et magistro, avanzi per decina Miglia 9 ¼, cioe quando se’andato tra ponente e maestro, cioe per mezzo vento, 10 miglia, sara’andato per ponente Miglia 9 ¼, et allargheratti per diecina Miglia <meno> 1/5.
You have to sail forward ponente but you cannot manage, you sail 2 quarters less ponente, between ponente and magistro, for each 10 miles you sail forward 9 ¼, that is, when you sail between ponente and magistro, that is a half wind, each 10 miles, you will have gone forward ponente for 9 ¼ and you will have sailed 1/5 less 4 miles each 10 miles.
E se ttu vai 3 quarte meno di ponente, che e quarte di maestro verso ponente, dove e questo segnale, 2 (il segnale e omesso), avanzerai in somigliante modo Miglia 8 1/3 per decina et alargheratti Miglia 5 ½ per decina. E se vai 4 quarte meno di ponente, cioe per maestro, che sono uno vento intero, avanzerai per diecina Miglia 7 et alargherati per 10 decine Miglia 7, cioe quando sarai andato per maestro Miglia 10, sarai andato per diritto per tuo cammino, cioe diritto per ponente, Miglia 7, et questo s’intende cominciando le miglie la ruota, cioe dal un punto della ruota.
And if you sail 3 quarters less ponente, which is a quarter from maestro towards ponente, where this sign is 2 (the sign is omitted), you will sail in a similar way, 8 1/3 miles forward and 5 ½ miles wide each 10 miles. If you sail 4 quarters less ponente, that is towards maestro, which is a complete wind, you will sail 7 miles forward each 10 miles and you will have sailed 7 miles wide each 10 miles, in other words when you have sailed 10 miles forward maestro, you will have sailed straight on your journey, that is 7 miles forward ponente, and that means starting counting miles along the wheel that is from a point along the wheel.
E ancora se ttu vuoi o dei andare per ponente et vai quarta meno per maestro verso tramontana dove e questo segnale // , che sono 5 quarte, avanzi per decina Miglia 5 ½ et alargherati per decina Miglia 8 1/3. E se ttu debbi andare verso ponente e vai inverso maestro et tramontana dove e questo segnale…, che sono 6 quarte, avanzi avanzi (sic) per decina Miglia 4 meno 1/5 et alargati per decina Miglia 9 ¼.
Furthermore, if you want or have to sail forward ponente and you are sailing a quarter less maestro towards tramontana where this sign is //, which are 5 quarters, for each ten miles you sail 5 ½ miles forward and 8 1/3 miles wide. If you have to go towards ponente but in fact you sail towards maestro and tramontana where this sign is…, which are 6 quarters, each 10 miles you sail 1/5 less 4 forward and 9 ¼ miles wide.
E se ttu andare per ponente e vai quarta di tramontana verso maestro, che ssono 7 quarte, avanzi per decina Miglia 2 et alarghati Miglia 10 meno 1/5. E se ttu vai per tramontana che sono 2 venti, cioe 8 quarte e sse sopra la crocie, tanto quanto andrai tanto t’alargherai et non avanzerai niente.
If you have to sail ponente and you are sailing a quarter of tramontana towards maestro, which are 7 quarters, each 10 miles you sail 2 miles forward and 1/5 less 10 miles wide. If you sail tramontana, which are 2 winds, that is 8 quarteres and you are on the cross, you will sail forward as much as wide and you will not proceed.
L’avanzare s’intende quando tu debba andare per uno vento diritto et diciamo per ponente e vai quarta meno di ponente e se’andato 10 miglia quando e sse’andato quarta meno di ponente Miglia 10. E ttu ( page c 203v) squadri verso di ponente, saresti andato Miglia 10 meno 1/5, et cosi s’intende di quante quarte fossono come dette abbiamo di sopra.
Sailing forward means you have to sail forward on a straight wind say for example forward ponente, and you are sailing a quarter less ponente and you have sailed 10 miles, when you have sailed a quarter less towards ponente for ten miles. And you go ninety degrees towards ponente you would have sailed 1/5 less 10 miles, so you understand how many quarters we have mentioned above.
Allargar s’intende cosi. Cioe noi dobbiamo andare per ponente et andiamo quarta meno da ponente verso maestro et sono alargato due Miglia in questo modo: noi siamo andati 10 miglia in quarta meno di ponente onde se io misurassi dalla linea di quarta meno di ponente in capo delle 10 miglia troverei 2 miglia insino alla linea di ponente dove sono questi due segni /../. segniati et chome abiamo mostrata questa regoa per lo ponente, cosi s’intende di tutti gli altri venti. E sempre quando tu dei andare per uno vento e ttu vai 8 quarte meno, che sono 2 venti, non puoi avanzare nulla, percio che tanto quanto andrai tanto t’alargherai percio che vai suso per la crocie non puoi navigare.
Sailing wide means, we have to sail towards ponente and we sail a quarter less from ponente towards maestro and so we have sailed 2 miles wide: we have sailed 10 miles forward a quarter less ponente, so if I measure from the line of ponente where these two signs /../ are and as we have shown this rule for ponente it is the same for all other winds. And always when you have to sail forward on a certain wind and you sail 8 quarters less ( than that wind), which are 2 winds, you won’t be able to proceed, because for as much as you sail forward you sail wide, therefore if you sail as a cross (at 90 degrees) you will not be able to proceed.
E debbi sapere che sempre quando dei andare per uno vento et tu vai meno tutto uno vento intero, tanto quanto avanzi per decina tanto t’alargherai per decina. Verbi gratia: noi vogliamo andare per ponente et noi andiamo per maestro che e uno vento intero, dunque alargherei 7 peer decina et alarghero 7 per decina.
You must always know that if you have to sail on a wind but you are sailing one complete wind less, each 10 (miles) you will sail the same distance forward and wide. For example: if we want to sail ponente but we sail forward maestro that is an entire wind, we will be sailing 7 miles forward and 7 miles wide each 10 (miles).
E quando tu se’andato meno di tuo viaggio uno vento intero di poi vai meno 5 quarte, si vai per positione, cioe tanto quanto avanzi prima per decina tanto t’alargherai per decina. E tanto quanto t’alargherai per decina tanto avanzi per decina. Verbi gratia: noi volemo andare per ponente et andiamo quarta di maestro verso ponente che ssono tre quarte meno di ponente, avanzerai Miglia 8 1/3 per decina et alargherati Miglia 5 ½ per decina onde se dovrai andare per ponente et vai 5 quarte meno cioe quarta di maestro verso tramontana, avanzerai tanto quanto t’alargherai prima, cioe Miglia 5 ½ per decina et alargherati tanto quanto avanzasti prima, cioe Miglia 8 1/3 per decina.
When for your journey you sail one entire wind less, then you sail at 5 quarters less, your position will be, each 10 (miles0 you will sail forward as much as you sail wide. And for as much you sail wide you sail forward each ten. For example: we want to sail ponente but we sail a quarter of maestro forward ponente that are 3 quarters less ponente, each 10 you will sail 8 1/3 miles forward and 5 ½ miles wide, instead if you want to sail ponente but you are sailing 5 quarters less, that is quarter of maestro towards tramontana, you will sail forward as much as you will sail wide, that is 10 (miles) 5 ½ miles forward and the same distance wide as much as you sailed earlier, that is 8 1/3 miles each 10 (miles).
E quando andasti intra ponente e maestro avanzasti Miglia 9 ¼ per decina et alargheresti 4 miglia meno 1/5, dunque quando andrai intra maestro et tramontana sicome avanzavi Miglia 9 ¼ cosi t’alargherai Miglia 9 ¼ per decina, et sicme t’alargavi 4 meno 1/5 decina cosi avanzerai 4 meno 1/5 et quando andavamo quarto meno ponente verso maestro avanzava 10 meno 1/5 per decina e alargaviti 2 per decina et cosi nel- la sua opositione. E quando andro quarta di tramontana verso lo maestro che ssono 7 quarte meno di ponente sicome avanzava 10 meno 1/5 per decina cosi m’alarghero 10 meno di ponente sicome avanzava 10 meno 1/5 per decina et sicome m’alargava mi- glia 2 per decina cosi avanzero Miglia 2 per decina.
When sailing between ponente and maestro each 10 you will sail 9 ¼ miles forward and 1/5th less than 4 miles wide, therefore when you sail between maestro and tramontana each ten you proceed 9 ¼ miles and 9 ¼ miles wide, and as you will sail 1/5th less than 4 miles wide each 10, you will sail 1/5th less 4 miles forward and when we have sailed a quarter less ponente towards maestro, we sailed 1/5 less than 10 forward each 10 and we sailed 2 miles wide each 10, the same in the opposite direction. And when I sail a quarter of tramontana towards maestro, that is 7 quarters less ponente, I sail 1/5 less than 10 forward and each 10 and I will sail 1/5 less than 10 wide each 10 miles as I sail 2 miles wide each 10, I will sail 2 miles forward each 10 miles.
E questa regola e pre sad a ponente percio quando dico 2 o tre piu quarte si s’intende da ponente, essendo questa regola del ponente, si s’intenda qualunque vento noi volessimo dire.
This rule is taken (given) from ponente therefore when I say 2 or 3 (or) more quarters I mean counting from ponente, being this rule of ponente, we mean the same thing for any wind.
Io v’o ditto della Tavola da navichare, ora vi voglio dire del quadrante come apresso vedrai per disegnio et poi per scrttura, come vedrai di sotto col nome d’Iddio et della sua Santissima Madre Verigine Maria.
I have told you about the sailing steering wheel chart for navigation, now I want to explain the quadrant as you can see in the drawing here below and in the following written paragraphs, as you will see below with the name of God and his holy mother the Virgin Mary.
Del quartiere aparteniente al mapamondo per mostrare quanto a da una citta a un’altra, Re. LVII
We write about the quarter of the globe to show the distance from one town to another.
Questo quadrante overo figura e fatta per mostrare quanto a da una citta a un’altra per file di cota. E diremo cosi: questo quartiere s’alata et non piu, cioe tra occidente et tra la citta d’Arin, overo dalla linea d’Arin al Traton movendosi dalla ditta linea cosi segniata 0 et andando verso l’arco dell’astremita dell’altra cosi segniata //, tanto si dicie longitude e de converse latitude. E nota che tanti gradi a punto et cosi grandi l’uno come l’altro, cioe 90 sono ciascuna linea retta, chef anno ad angolo retta alla citta d’Arin, come l’archo pogniamo che nella rapresentatione para piu grande l’archo che lle linea, percio che lla linea dee essere giu bassa e levata in archo ma non si puo mostrare se non materialmente, percio ciascuno quartiere sie 90 gradi, ma chi forasse per lo cientro dell’altra farebbe gradi 114 6/11, percio che va diamitralmente, ma ccio che nnoi parliamo di sopra l’astremita dell’altra siccome mostra la spera corporea. E questo quartiere e segniato a cinquini. E dove dicie 90, cioe inn occidente poi dicie 5 et andare verso la citta d”Arin e de converse, et cosi dell’altra linea, verbi gratia.
The quadrant or figure is drawn to measure how far is one town from another referring to “file di cota”. We will explain this way: this quarter expands, but not any further, between west and the town of Arin. That is from the line of Arin to Traton moving from this line marked with the sign 0, and going towards the arch of the other end, marked with this sign //,the first is called longitude and the other latitude. Please note that there are degrees identified by points which are the same size, that is 90 in each straight line, which makes a right angle with the city of Arin, we assume that in the representation, the arch will seem bigger than the line, so the line must be lower and changed into an arch but this cannot be shown if not physically, therefore each quarter is 90 degrees, but what would pass through the centre of the other would make 114 6/11, therefore it goes to the other end passing through the centre, as we say over the opposite end as it is shown by the physical sphere. And this quarter is marked by sets of 5. And where 90 is marked, that is the west then it says 5 and to go towards the town of Arin and the same on the other line, for example.
Gierusalem sie di l’atezza gradi 33 1/3 et di longitudine gradi 56 2/3, per noi Gierusalem in qual parte de’ essers dell’altra, cioe nel ditto quartiere, per ragione questo e difficile a mostrare per figura piana, percio che I gradi non dicono vero, dico cosi uno quartiere di palla ritonda per ongni verso 90 gradi e una linea si vuole cioe l’altezza et vieni verso il Taron che e gradi 33 1/3 et un altro si muove da l’arco dove finisce thtto l’ocidente, la quale e lunga gradi 56 2/3 dove s’accozeranno insieme, et quello luogo sara Gierusalem. Farai cosi; puolo fare materialmente, prendi una spera tagliata a 90 per quartiere et prendi due fili, l’uno sia gradi 33 1/3 et l’altro gradi 56 2/3 di simili gradi che sono nella spera overo nella palla, et poi metti il capo dell’uno filo sopra la linea equinotiale per filo di rota diritto vesro l’archo occidentale et vada verso la linea d’Arin et di Atraone ), et dove I capi s’accozano insieme quivi s’accoza Gierusalem.
Suppose Jerusalem is at the height of 33 1/3 degrees and latitude 56 2/3 degrees, for us where Jerusalem would be in that mentioned quarter, it is obviously difficult to show on a flat dimension, as the degrees do not show the real, I call a quarter of a ball for every 90 degrees and a line is needed which is the height and you go towards Taron which is 33 1/3 degrees and another one moves from the arch where the west ends, which is 56 2/3 degrees where they meet, and in this position Jerusalem is. You will do as follows: to make it practically take a globe cut it at 90 in quarters and take two strings, one at 33.1/3 degrees and the other at 56 2/3 degrees as they are in the globe that is in the ball, then place the string end over the equinox line and pull the string straight towards the western arch and continue towards the line of Arin and Altraone 0, and where the ends meet there is Jerusalem.
Et cosi di tutte alter cittada et luoghi. Ma ora io lo mostro per regola: prima diremo quandro aria trovato nella palla ritonda dove e Gierusalem, e ttu fa nota in sulla palla, et poi se ttu vuoi sapere quanto a da Ierusalem a Parigi vedi second che ai fatto di Ierusalem, dove e Parigi e ffa nota sopra alla palla. E poi trai sopra la linea da una linea dall’una all’altra et poi misura detta nota, cioe di Gierusalem et di Parigi, et misura di simili gradi della grandezza di gradi della palla, et tanti gradi ara da Gierusalem a Parigi, e poi recha I gradi alle leghe o vuoi Miglia sicome ti mostra adrieto nelle carte …. Ora lo mostriamo per giometria.
And you do the same for all the other towns and places. But now I am going to show the rule: first we explain where to find Jerusalem on the round ball, and you mark the ball, and then if you want to know the distance between Jerusalem and Paris see what you have done for Jerusalem and do the same for Paris and mark it on the ball. Then pull a line from one place to the other and then measure this line, that is the line between Jerusalem and Paris, and measure the degrees according to the dimension of the ball degrees, and that number of degrees will be between Jerusalem and Paris then turn the degrees into leagues or miles aas shown in the previous maps……. Now we show it in geometry.
E nota che altitudine s’intende senpre dalla linea equinoctiale verso settentrione. E latitude s’intende dall’astremita della terra dov’e questo // andando verso meridie. Verbi gratia: una citta a di longitude 70 gradi dunque e 20 gradi presso la linea di meridie. E meridionale di ciascuno paese si vuole tanto dire quando il sole e ffinito di quello traccio, e quello archo che ‘l sole fa apopunto a mezzogiorno, quello e archo meridionale in quello paese, ma archo meridionale di tutta la terra sie la circunferenzia che ttaglia per lo cientro di mezzo da meridione a settentrione.
Please note that with altitude we always mean the equinox line towards north. And with latitude we mean (the line) from the far end of earth where this symbol // is, going towards south (meridie). For example: one city at a longitude of 70 degrees is 20 degrees on the southern (meridie) line. And the southern part of each country is where the sun ends in that path, and that is the arch made by the sun at noon, that is the southern arch in that country, but (also) the southern arch of the whole earth is the circumference that cuts the centre from south to north.
E nota che ‘l di natural nonn e iguali per tutta la terra percio che la session de’ segni non monta iguali che gradi del zodiacho non vanno iguali coll’equinotiale. E nota che di giorno nel miraglio non si pou vedere nulla stella salvo che Venus et Mercurio percio che ssono di sotto al sole. E nota che quando la luna si novella se vuoi sapere se dara pioggia o sereno guarda quello punto che rinuova quale e il segnoi dell’asciendente e sse gli e Venus o lluna dara pioggia percio che ssono freddi et humidi et cosi degli altri. E guard ail segniale dove si rinuova la luna, sse la e palida significa pioggia, se ll’e rossa significa vento, se ll’e biancha et chiara significa sereno et buono tempo. E guarda alle quadre cioe 7 e 14 e 21 e 28 e non guadare re la quintadecima, siccome parla nella propozione de’pianeti si diremo che del diamitro del corpo della luna sie 948 miglia e mezzo il diametro del corpo del sole e Miglia 17850 e 4000 gomito sono uno miglio comunale et multiprico il doppio di 948, cioe 1896, per 3 1/7 che fanno 5958 4/7, e tanto gira tutto il corpo della luna, cioe Miglia 5958 4/7. E multiprica il doppio di 17850, cioe 35700 per 3 1/7 che fanno 112200. E second Tolomeo il corpo della terra gira 24000 di Miglia come parlo nel 27 e nel 28.
Please note that the day is not the same in all the earth therefore the set of signs is not the same and the degrees of the zodiac are not equal to the equinox.
Please note that at midday it is not possible to see any star except Venus and Mercury as they are below the sun. Please note that at new moon if you want to know if it will rain or it will be sunny, look at the point where the zodiac sign is ascendant, if it is towards Venus or Moon it will rain because they are cold and humid and it will be the same for the others. And look where the moon renews, if it is pale it will rain, if it is red it will be windy, if it is white and clear it will be cloudless and good weather. And look at the squared, that is 7 and 24 and 21 and 28 and do not consider the 15th, as it is about the proportion of the planets we will say that half diameter of th moon is 948 miles and half diameter of the sun is 17850 miles and 4000 elbows are one simple mile and I multiply the double of 948, that is 1896 by 3 1/7th which is 5958 4/7ths and this is how much the circumference of the moon, that is 5958 4/7ths. Multiply the double of 17850 that is 35700 by 3 1/7th which is 112200. According to Ptolemy the earth circumference is 24000 miles as I say at 27 and 28.
De Llatitudo di sapere quando e da una citta a un’altra Re. LVIIII
The latitude, to know how far a city is from another one Re. LVIIII
Questo e latitude come si mostra latitude et longitude delle terre. Prima diremo della citta d’Arin sie in sul cientro de’lata e sta di lungie a occi-dente 90 gradi e a settentrione 90 gradi e 90 oriente e 90 meridie. E tutto to l’abituro nostro e uno quartiere, cioe intra a settentrione et occidente. Il veracie occidente sia per linea della citta d’Arin infino a occidente, veramente ciascuna citta sia suo occidente in questo modo. In qualunque modo e la citta sia il suo occidente l’opposito che andasse per la linea dirtta all’astremitade della terra, cioe l’archo.
This is latitude, how latitude and longitude of any place on the earth are seen. First of all we will consider the town of Arin which is in the centre of the side and it is placed 90 degrees far from west and 90 degrees from east and 90 degrees from south. Our settlement is a quarter, located between north and west. The original west position is on the line with Arin towards west; actually each town is always to its west (to the west of Arin). In any position a town is placed it is always to its west the opposite is the arch that goes along the straight line to the other end of the earth. Diagram ChMa1D09.
Verbi gratia poni che questo segniale sia una cittade /c/ et quest oil suo occidente /o/ et tanto quanto e l’uno segniale dall’altro e tanta e di longitudine, si conta tanto quanto a dalla linea equinoctiale infino a quella terra andando per filo di rota verso settentrione o vuogli tanto quanto e alto il polo in quella terra.
For example, we suppose that this symbol /c/ represents a city and this symbol /o/ is its west, and the distance between the two symbols is its longitude, which is counted from the city to its west. And Latitude is measured from the equatorial line to that land (city) going along the arch towards north or (it is measured) how high is the pole of that land..
Latitudo si truova per lo quadrante sicome puoi vedere, ma longitude si truova per le tavole el piu veritiero longitude che ssia se ssi puote trvare quando e eclipsis in questo modo ma non tutto a un’ora sole quando eclipse lune sie per o universe mondo ma non tutto a un’ora ma quando eclipse sole e in alquante climate ma non e a un’ora.
Latitude is calculated (placed) on the quadrant as you can see, instead longitude is placed on tables and the most truthful longitude is when there is an eclipse if you have one (eclipse), but not at the same time in every place, it happens everywhere but not at the same time.
Verbi gratia, in Bruggia fa eclipsis a mezzogiorno, cioe a 6 ore del di, e a Vignone fu 9 ore di quello di, adunque di 3 ore v’e diferentia, e ogni ora si conta 15 gradi, adunque diremo second la proposta da Bruggia a Vignone sia 45 gradi di longitude et cosi a di tutte l’altre terre.
For example in Bruggia the eclipse is at midday, that is at the 6th hour of the day, instead in Vignone (the eclipse) is at the 9th hour of the same day, therefore it happens with 3 hours of difference, and for each hour 15 degrees are counted, therefore we can say as per our proposal that from Bruggia is 45 degrees of longitude to Vignone, and that is for all other lands (cities).
Questo sono longitudini di certe cittada famose et latitude sie scritto adietro a carte…. Et primamente diremo Gierusalem gradi 56, Gostantinoploi gradi 56, Allessandria gradi 51, Palermo gradi 37, Malta gradi 38, Cicilia dall’altro capo gradi 36, Babilonia gradi 78, Tolletta gradi 28, Corduba gradi 9. Vienna gradi 24m. 4, Cremona gradi 31, Parigi gradi 29m 29, Roma gradi 36m 25, Setta gradi 8, Cordoba gradi 9m 20, Almeria….
These are the longitudes of some famous cities, and latitude is written at the back of maps…. First of all we say that Jerusalem is 56 degrees, Constantinople 56 degrees, Alexandria 51 degrees, Palermo 37 degrees, Malta 38 degrees, Sicily, opposite side, 36 degrees, Babylon 78 degrees, Tolletta 28 degrees, Corduba 9 degrees, Vienne 24 degrees and 4 minutes, Cremona 31 degrees, Paris 29 degrees and 29 (minutes), Rome 36 degrees and 25 minutes, Ceuta 8 degrees, Cordoba 9 degrees and 20 minutes, Almeria….
CONCLUSION SECTION 4
By the time this text was written it appears that the ideas of geometrical mapping had advanced as the c.204v diagram, the quarter of the world indicates. The author wanted it to be a diagram of a curved quarter segment of the world as I have tried to reproduce as diagram ChMa1D08, but he has also become caught up in the fiction of Arin, this sometime mythical city. The fact that a table of longitudes was included would be a help to cartographers if it had been zeroed as a diagram from this information is hard to interpret. We know that tables of longitudes existed from the 12th century and this if complete would be a considerable aid. As this is within a treatise on the Abacus we can only assume the author was a mathematician with some knowledge, but he perpetuated the Marteloio myths..
The first and foremost conclusion is an unavoidable recognition that the mathematics were either not understood by these authors or that they just ignored the obvious errors which they were perpetuating.
How does a mathematician use a series of measures which are approximations of angles and produce end results which they know are promulgated by 100 miles, and then state that the end voyage is 98 4/5ths miles, when it is 100 miles. It should be clearly stated as such, or the figures noted as approximates and rectified to 100 miles as necessary.
It is easy to criticise, but the obvious errors are never mentioned and thus how did a simple mariner understand what he was actually sailing via these Marteloio. The problems are exacerbated of course when there are several tacks made in one journey.
It begs the questions, were they ever used, were they actually able to be used? Andreas Biancho uses the term mental mathematics, but it is perhaps expecting a great deal from a mariner when there are several tacks involved. But there was always an obvious solution as I have pointed out repeatedly. For a simple wind off course sail it’s opposite and sail the same distance to place you back at a point on your original course line. But if a mariner has common sense and can use the winds, if available, he can track back to the original course line far quicker depending upon the distance off course sailed.
I suggest that these are the figments of mathematician’s imagination; that is a development of theoretical geometry which has been applied to the sea for mariners to try to use but has been sorely misjudged by mariners as to its usefulness when simplicity would solve it all.
M J Ferrar August 2014.
Ramon Lull, Arbor scientiae venerabilis et caelitus illuminate patris. Page 69, Quaestiones foliorum, De quaestionibus Arithmetica and de quaestionibus Geometriae.
Ramon Lull, Ars magna generalis, Decima pars, Article 82, Geometry, de application fo. Xciii and Forma de navigatide fo. Xciiii, and in Undecima pars fo. Cxxii, de qstionibus navigationis.
Professor Raffaella Franci is Professor of Complementary Mathematics at Siena university, Italy and discovered a hitherto unknown document concerning the Marteloio. It was published in Bulletin of Mathematical Sciences, 30 (2), 2010, 133 -188, Excerpts from DA: Astronomy/Astrology in a treaty of Abacus in the first half of 15th C (MS. Magl. CI. XI 119 of the National library of Florence, Italy. See ???? section of Text.
Professor Raffaella Franci, Bulletin of Mathematical Sciences, 30 (2), 2010, 133-188.