238 44 EXTRACT FROM THE TREATISE ON NAVIGATION OF IL CAVAGLIERO ANTONIO PIGAFETTA. THE PREFACE OF AMORETTI, Tranflator of the Voyage into modern Italian and into French. HE Treatife on Navigation, which, in our manuscript is found at the end of the Voyage, is not affuredly a work calculated for the inftruction of navigators of the present day; nevertheless it deserves publication in my esteem, as much on account of the honor it does its author, as its ferving to throw light on the history of the human mind, by fhewing the progress made in the art of navigation at the commencement of the fixteenth century. All, acquainted with the sciences, at this time know the method by which the latitude and longitude are determined any where, even in the open fea, and are also apprized of the variation of the magnetic needle; but in the time of Pigafetta the knowledge of these matters was a mystery to all except the higher clafs of the learned. The nautical inftruments were the astrolabe and the compass, of the variations of which latter even pilots, in general, were ignorant, as is deduced from the fpeech of Magellan to his fquadron. Regiomontanus had indeed already invented his meteorofcopet, to determine the distances of places from each other, as well in longitude as in latitude; and by means of a fimilar inftrument it was that Amerigo Vefpucci, in 1499, after a tempeft in which the whole of thofe on board his veffel had loft their reckoning, afcertained his pofition in midst of the Atlantic Ocean, by an observation of the conjunction of the moon with Mars, which had been calculated by Regiomontanus himself for the latitude of Ferrara t. But the use of these inftruments, as well as fuch calculations, were fo little known, that Vefpucci was regarded by the ship's company as a wonderful man, to whom, in confequence, they gave the command of the veffel: he was afterwards entrusted with other grand enterprizes, in one of which he found occafion to give his name to the new continent. Now, these methods, with which few perfons at that time were acquainted, and of which Pigafetta had made himself master, are nearly the fame as those now in use. The latitude of a place is ascertained by taking the elevation of the pole at night, and by obfervations of that of the fun at noon. The elevation of the pole is found by that of some star the latitude of which is known, generally the polar ftar, which, in the space of twenty-four hours, defcribes a fmall circle round the pole. This circle was known to Pigafetta; and he was not affuredly very wrong in his statement, for its radius was 3° 17′ 37′′, notwithstanding it is now but 1° 46', the polar ftar approaching gradually towards the pole, after a rate which, in the lapfe of fo many years, has occafioned this difference. In order to find the vertical distance of the polar ftar from the pole, as now, it was the custom then to observe the position of some star about the polar, under the *See Book ii. of the Voyage of Pigafetta, page 323. + See the Introduction to above Voyage, parag. iii. and note. fame meridian, or making fome known angle with it. In the present day it is ufual to obferve the star y of Caffiopea, which is called the Girdle, and is nearly under the fame meridian. In the time of Pigafetta they observed the relation the polar ftar bore to the stars and y of the Leffer Bear, which form a triangle with the polar star and the pole. After which they faftened a triangular rule on the centre, or pole, of the astrolabe, by the obtufe angle on which it turned t. Even now a rule nearly fimilar is ufed, and the inftrument ufed for this purpose is called nocturlabe 1. But, fpite of the different pofition and distance of the stars, and notwithstanding the inftruments used in the present day are diffimilar to those at that time adopted, it is visible that the method of afcertaining the latitude by the height of the pole at night, and of the fun by day, are ftill the fame; and these methods it is that our author teaches for finding the latitude at fea. With respect to the afcertainment of the longitude, Meffieurs de la Lande and Bougainville conceive the method by taking the horary angles of the moon is the safest and most convenient §; and Triefneker ||, with Bouguer ¶, affirm, that the best method is by the conjunction with, and eclipfes of the stars by the moon. Our author recommends the fame in the two firft of the three methods he gives for this purpose. And as he fails to speak of the mode of finding the longitude by folar eclipfes, it is evident that with this he was unacquainted, and confequently that he did not fee Magellan practice it at the river of Sta. Cruz, as Caftagneda affirms **. I am aware that all the obfervations made were computed upon the almanacks of the day, and that these almanacks were far from calculating with that precifion which is admired in the ephemerides of the present time the different phenomena of the heavens: I know that the lunar tables were then much lefs perfect than they now are, and that Pigafetta had not the advantage of being enabled, as the telescope had not yet been invented, to obferve the eclipses of the fatellites of Jupiter. All refults then rested on obfervations made with very imperfect inftruments, and efpecially the aftrolabe, of which Pigafetta often speaks, the meteoroscope, the torquetum, the backstaff, and the universal circle, inftruments and machines which were neither certain in their refults nor easy or commodious to use, as are now the fextant of Hadley, the English quadrant, the circle of Borda, and other inftruments fo formed that the motion of the veffel is no impediment to their being ufed, nor capable of affecting their exactitude. The correctnefs of the refult of obfervations for determining the longitude neceffarily depends on the precifeness of the time at which the observations are made, and the relation it bears to that of the country the longitude of which is known, or fuppofed to be known at that period the only means of determining the hour was by the fand glafs, in the conftruction and ufe of which it is impoffible to be exact, fo that indeed Pigafetta himself did not rely on it. But at prefent we have excellent chronometers and fea-watches, which are not liable to any variation, or which, if they experience any, are readily corrected. By means of thefe it is that we obtain that precifion of time which allows of the longitudinal distance being afcertained with the utmost exactitude, a matter as difficult until this invention as it was material for navigators; and for the discovery of *Bouguer, Traité de Navigation. + These machines are to be seen in Apiano. Aftronomicum Cæfareum; and in Lucini, Arcano del mare. Dictionnaire de la Marine, artic. Nocturlabe, where the figure of this inftrument is given. Bougainville Voyage, tome xi. p. 65. Allgemeine Geogr. Ephem. Jan. 1798. Traité de Navigation. ** Page xxxix. note ii. which Spain and Holland, and after them England and France, have proffered, and already given very confiderable rewards. It is therefore evident that Pigafetta, having no exact data, could only give doubtful refults; but this does not take away from the aftronomers and navigators of his time the merit of having conceived, nor from our author that of having practised, methods which, in modern times, have been brought to perfection, by removing the uncertainty refulting from the use of bad instruments, and a want of correct aftronomical and phyfical obfervations. The celebrated navigator, Bougainville, fome fhort time back read a memoir to the National Institute of Paris, in which he drew a comparison between the means poffeffed by Magellan and the immortal Cook: were I to repeat his remarks, we should, without doubt fee that, if Cook made more extenfive and important voyages, Magellan, deftitute as he was of the grand means poffeffed by the English Commodore, undertook a voyage which exacted a man of far fuperior talents to his contemporaries, as well as of much greater energy of character. And, as Pigafetta wrote his treatife after the Voyage †, it is highly probable that he received from Magellan himfelf the nautical inftructions he has given, and that this captain-general was taught them by the astronomer Faleiro, whose knowledge was fo admirable in his time as to caufe him to be fufpected of being infpired by fome demon. One cannot, it is true, attribute praife to our author when he attempts to explain the movements of the planets and stars by the fyftem of Ptolemy, the abfurdity of which is now demonftrated; but on the other hand this error cannot be confidered as blameable in him, when we reflect, that it was then in measure confecrated, and call to mind the misfortunes of Galileo, which were owing to his daring to oppose the system of Copernicus, a century even later. Pigafetta was moreover in error when he pretended to have difcovered the longitude by means of the variation of the magnetic needle; but even this error is excufable on referring to the age in which he lived, and confidering that he was deceived by a falfe theory; for he imagined that there were in the heavens fome fixed spot towards which the needle conftantly pointed; and he was in fome measure confirmed in his opinion by the fact; for at that time the magnetic needle on the first meridian, fixed by Ptolemy at the island of Ferro §, was fubject to little, if any deviation, and in other places the degrees of longitude correfponded with the degrees of deviation of the needle from the north. Add to all this that the author of the Arcano del Mare, a claffical book on navigation, among other means of finding the longitude at fea, recommends the paying attention to the variation of the compafs ; and that the celebrated Halley, after attentively noticing the obfervations of navigators on the deviation of the needle, conceived it poffible to form circles by means of which the longitude of places might be determined by the variation, he himself being ignorant that this variation is progreffive, and inconftant in its progreffion, and that confequently it cannot be fubjected to calculation; and moreover that computation, as was observed Allgemeine Geogr. Ephem. Decemb. 1798, p. 553. In the Treatife he quotes his Voyage, in which he fpeaks of the ftars round the fouthern pole. a better. By the table of the declenfions of the magnetic needle, publifhed by the learned Lambert in the ephemerides of Berlin, (Aftronomische Jahrbuch for the year 1779) it will be found, by means of a short calculation, that at the beginning of the fixteenth century the magnetic equator, or the of deviation, was near the island of Teneriffe. At prefent it is diftant, and every day becomes further from it. M. de Bougainville found the declension of the needle in this part to be 14° 41' W.; and Staunton, who accompanied Lord Macartney on his Embaffy to China, 17° 35′ W. Tome i. p. xi. by by Cook*, will always be vague, on account of the variation in the fame place and at the fame time being different with different needles. Among the means of ascertaining every day the longitude of any spot while at sea, Pigafetta does not mention the log-book or log,- -not because he was unacquainted with it; for he obferves that they measured the way they made by means of the chain †, which is the fame thing; but probably because he knew the inadequacy of this mode, especially in navigating from one parallel to the other, in the direction of fecondary winds, and where borne away by currents the rate of which cannot be duly ascertained. After indicating the means of determining the latitude, Pigafetta gives a long catalogue of the latitudes, boreal as well as auftral of the countries, ports, promontories, &c. known to navigators in his time; but this catalogue, being merely a copy of what may be seen in books of geography of the fixteenth century, I have though.t it unneceffary to publish. I fhould occafionally have found it highly difficult to comprehend this Treatife on Navigation, adapted by the author to the information, but especially to the inftruments of his time, but for the mufæum of our library, which furnished me with astrolabes, compaffes, the machine pointing out the winds, and other inftruments and books used by navigators at the commencement of the fixteenth century. By comparing these inftruments and drawings in the books with what he wrote, I fucceeded at length in comprehending a number of words and phrafes made use of by him. Still I think it just to declare to the reader, that, generally fpeaking, I have much abridged this treatise, not only because in many parts it contained trivial information, and that fometimes repeated, but also, and that more especially, on account of the text being frequently unintelligible, more, I have no doubt, owing to the negligence of the copyift, than that of the author. I thought it better, where this has been the cafe, wholly to omit what was not eafy of comprehenfion than to torture my brain with endeavours at gueffing the meaning of the author, and putting in his mouth poffibly words that he never uttered. EXTRACT OF THE TREATISE ON NAVIGATION OF PIGAFETTA. Defcription of the Armillary Sphere. THE armillary sphere, the defign of which Pigafetta promifes to give, is used by him to explain the fyftem of the univerfe according to Ptolemy, and might be used as an astrolabe; for on the top of it is a kind of femicircle, or ring, which ferves for its fufpenfion when employed as an aftrolabe. Pigafetta begins his treatife with a defcription of the fyftem of the world, in imitation of all thofe who have preceded or followed him in writing on the elements of the art of navigation. "The earth," he fays, "is round; it is fufpended and motionlefs in midst of the celeftial bodies. The primum mobile is refident in the axis of the two poles, the arctic and antarctic; which two poles are fuppofed to be united through the poles of *Third Voyage, book i. VOL. XI. +Book ii. of this Voyage. 3D the the earth this axis revolves from east to weft, and in its revolution carries with it the planets and all the ftars. Befides this there is an eighth sphere, the poles of which are 23° 33' from the equinoctial line; the axis of this fphere turns from weft to east. "The circumference of the earth is fuppofed to be divided into three hundred and fixty degrees, and to each degree are affigned seventeen leagues and a half: the circumference of the earth is confequently fix thousand three hundred leagues. The league by land is three miles, the fea-league is fourt. The ten circles of the armillary fphere, the fix larger of which have the fame centre as the earth, ferve to determine the climates and geographical fcite of places. The ecliptic fhews the course of the fun and planets. The two tropics point out the diftance to which the fun diverges from the equator, northward in fummer, and in winter fouthward. The meridian, ever variable as it paffes through all the point of the equator, cutting it vertically, defignates the longitudes, and on this circle it is that the latitudes are marked." Of the Latitude. After a description of the fyftem of Ptolemy, and after explaining every part of the armillary sphere, the author teaches the manner of taking the height of the pole, by which means the latitude is found. He places the pole at o and the equator at 90°‡. It is well known that at prefent we reckon from o to 90, beginning from the equator and proceeding to the pole. "I. The polar ftar," he says, " is not precisely on the point corresponding with the axis of the earth, but like all the other stars it revolves about this point. In order to know the true pofition of the polar star with respect to the pole, that of the guards * The declination of the ecliptic, which answers to the poles of the eighth sphere of our author, is now 23° 28' 30". + Suppofing the terreftrial globe under the equator to be fo divided that half its circumference should confift of land and half of water, and giving confequently to each league three miles and a half, we fhall have for the circumference of the globe under the equator twenty-two thousand and fifty miles; a fum differing but little from that which refults from giving fixty miles to each degree, which makes the circumference twenty-one thousand fix hundred miles. AMORETTI. Here the Italian editor wholly mistakes his author, and fhews greater ignorance than could have been fuppofed in a librarian having accefs to works on navigation, and digefting a treatife on this fcience. All that was meant by Pigafetta in his obfervation that a league by land is but three miles, while a league at fea is four, is to admonish the reader that in his computation of the circumference of the earth at fix thou fand three hundred leagues, he means fea and not land leagues, for if the latter were taken the circumference would be eight thousand four hundred. That this is the cafe is evidently clear from his obferving that the fea league is of fuch length that feventeen and a half go to a degree, confequently feventy miles. Now the degree of longitude on the equator is 69, English miles, and the circumference of the globe 24,902 of thefe miles, which comes very nigh the computation of Pigafetta. Geographical miles were utterly out of the queftion with him, (thofe to which Amoretti adverts in computing 60 to a degree). It is not however equally evident what mile he alludes to when he ftates the league to confift of four; the degree measures 67, of the prefent miles of Milan, 68, of thofe of Tufcany, 60,1% of those of Venice, and 74,1 of thofe of Rome. ENG. TR. 25 TOO 62 This again is another error on the part of Amoretti, which attention to the text of the voyage in every inftance where the latitudes are marked will clearly fhew; it is also evidently a mif-statement from the tenor of the two inftructions which follow for finding the latitude, first by an obfervation of the polar ftar, and fecondly of the fun. Poffibly, though he fays he declined bewildering his brain in endeavouring to folve fome apparently incomprehenfible parts of this treatise, Amoretti did not defift from the attempt until it had become confiderably clouded; at least thus much may fairly be conjectured from the ftatements which have produced this and the preceding note. ENG. TR. muft |