152 



NAVIGATION. 



decessors, visited the Atlantic coasts of Europe, the 

 British isles, and, pursuing the grand idea which 

 afterwards led tin- Portuguese to India, discovered a 

 vast extent of the western coast of Africa. Pliny 

 t vcii states that Hanno completed its circumnaviga- 

 tion, and returned home by the tied sea. Had not 

 Carthage prematurely fallen beneath the rivalry of a 

 nation braver and more barbarous, Vasco da Gama 

 might have had to seek laurels elsewhere than by 

 sailing first to India, and even Columbus been spared 

 the most brilliant and enviable of all the achieve- 

 ments of navigation, the discovery of the New 

 World. The art of navigation gained nothing after 

 the foil of Carthage ; ana the invasion of the north- 

 ern barbarians effectually extinguished the few 

 gleams of science which had survived her catas- 

 trophies. Every thing remained stationary for cen- 

 turies, until the returning day of civilization began 

 once more to dawn upon the world. 



It was not until the close of the twelfth century, 

 that man became sensible of the existence of the 

 most singular property which an all-wise and all- 

 beneficent Creator has provided to be his guide upon 

 the deep ; nor until a still later period, that the 

 genius to improve it the gift of the same good 

 Being at length rendered it available to so noble a 

 purpose. We allude to the polarity of the magnet, 

 and the invention of the mariner's compass. The 

 property of that mysterious mineral to attract iron 

 was early known to the Greeks and Chinese ; but the 

 fer more singular one of assuming a particular direc- 

 tion, was not even suspected. Pliny himself, who 

 records every thing known or fancied in his time 

 concerning the magnet, makes no allusion to its 

 polarity. The first accounts of this speak of it as 

 known in the twelfth century, and that mariners 

 sometimes made use of it to ascertain their course. 

 Of the mariner's compass, we can only say that it 

 was either invented or revived in 1302, by one 

 Flavio Gioia, an obscure individual in the kingdom 

 of Naples ; and even this is not known with cer- 

 tainty. While the heroes of the remotest times come 

 down to us, not only with an accurate account of 

 battles fought and thousands slain, but with a minute 

 detail of their private lives, and most insignificant 



Seculiarities, posterity is at a loss to know whom to 

 less for a recent discovery, of all others the most 

 useful in its results, the most important in its influ- 

 ence upon the destinies of man. The effects of this 

 discovery upon navigation were not, however, im- 

 mediate ; for the mariner, as much as any one the 

 slave of habit, could not at once appreciate and con- 

 fide in the excellence of his new guide. This is the 

 only excuse for the uncertainty which hangs about 

 the dentity of the discoverer. The experience of 

 half a century, however, showed the value of this 

 new assistant. Navigation now assumed a bolder 

 character. Prince Henry of Portugal, son of king 

 John, having gained a brilliant reputation in a war 

 with the Moors, turned from these fierce pursuits to 

 the more congenial one of science. Retiring from 

 court, he established himself in a retreat upon the 

 promontory of St Vincent, and, calling round him 

 astronomers and mathematicians from every nation, 

 lie collected and systematized all the science of the 

 day. Nor were his researches of a mere speculative 

 character ; they were directed to enlighten the field 

 of discovery in which he was engaged, in search of a 

 nearer route to India, and which, though he attained 

 not the grand object of his ambition, repaid him well 

 by the inferior discoveries to which it led. It was 

 to aid these enterprises that he caused charts to be 



drawn, which, thbugh they involved the monstrous 

 supposition of the earth's being an extended plane, 



were of no inconsiderable use to the navigator, as 



they brought together whatever was known of the rela 

 live position of the different points of the earth, and 

 enabled him to see, at a single glance, as in a pic- 

 ture, not only the direction of the port which he 

 desired to visit, but also the various coasts, rocks, 

 and quicksands, to be avoided in the way. He also 

 invented the astrolabe, which was simply a quadran- 

 tal arch, graduated at the rim into degrees and half 

 degrees, and by directing one edge of which towards 

 the heavenly body whose altitude it was desired to 

 measure, a plummet suspended from the centre was 

 made to mark the angle of elevation. This was 

 used at first to discover the latitude from the eleva- 

 tion of the pole star ; for, as that star is in the hori- 

 zon when viewed from the equator, and rises grad- 

 ually in approaching the pole, so that it would at 

 length become vertical, it follows, that the elevation 

 is always equal to the observer's distance from the 

 equator, which is the latitude. The error resulting 

 from the star's not being exactly polar, was of little 

 note in those primitive days of the art. Soon after, 

 by causing tables of the sun's declination to be com- 

 puted, prince Henry enabled the mariner to deduce 

 his latitude more correctly from the meridian altitude 

 of that star. Yet all these improvements, though 

 they added much to what was already known, left 

 the art in its infancy. Columbus was the most 

 accurate navigator of his day ; still we find him often 

 making an error of so many degrees in his latitude, 

 that the mistake of an equal number of minutes 

 would not be excused in a modern navigator. To 

 mention one of many instances, he places San Sal- 

 vador three degrees north of its true, position. But 

 if Columbus made his discovery with such imperfect 

 means, the greater was his merit : to him belongs the 

 credit, by pushing boldly forth amid the uncertainties 

 of the ocean, of forcing navigation, as well as ship- 

 building, to provide against new difficulties, and 

 march rapidly onwards in the career of improvement. 

 From the moment that the hitherto hidden mys- 

 teries of the ocean were thus solved, we find im- 

 provements and inventions multiplying in rapid suc- 

 cession : First, the log is introduced, to measure the 

 ship's rate of sailing : Nunes, a Portuguese mathemati- 

 cian, next shows that the shortest distance from place 

 to place upon the surface of the globe, must always be 

 along a great circle of the sphere: he also proves the 

 fallacy of the plane chart ; Gerard Mercator, a 

 Fleming, next suggests the idea of extending the 

 meridian lines on the plane chart, in receding from 

 the equator, in a ratio equal to the error occasioned 

 by supposing the meridian s parallel, instead of 

 gradually converging as they do towards the poles. 

 By this means, the advantage of a plane surface was 

 retained, without the error of the old chart, or the 

 inconvenience and imperfection of the globular pro- 

 jection. Wright, an Englishman, improving the 

 suggestion of Mercator, calculates a table of merid- 

 ional parts, increasing the length of the arches of 

 meridians in due proportion towards the pole , and 

 furnishes, thereby, data to determine, in any latitude, 

 the difference of longitude from the departure, or 

 distance sailed east or west. At the same time, 

 Napier's invention of logarithms wonderfully dimin- 

 ishes the labour of calculation, enabling the mathe- 

 matician, by their help, to substitute for the tedious 

 operations of multiplication and division, the simpler 

 ones of addition and subtraction. Now, too. Gunter 

 presents the seaman with his admirable scale, con- 

 taining the logarithmic lines, by aid of which and a 

 pair of dividers, all the problems of geometry are 

 easily and accurately performed. The circumference 

 of the earth is ascertained by measuring a given por- 

 tion of its arch; and the length of a degree being 

 known, the log-line is marked accordingly. The 



