« ForrigeFortsæt »
stadium, which, according to M. Le Roy and M. Freret, is 114 toifes, would make the difference ftill greater; as, on this hypothefis, the error would amount to twenty-three thousand toifes in a degree.
M. GOSSELIN follows the common opinion, that Eratofthenes compiled much of his fyftem from the works of preceding geographers; in which refpect, his office, of librarian to the Ptolemies, afforded him peculiar advantages; and it is obferved that there are, in the fragments of his works which are tranfmitted to us, a mixture both of truths and errors, that cannot well be referred to the fame writer, nor even to the fame period of fcience.
As Eratofthenes appears to have known nothing of the projection of the fphere, his maps must have been plane charts, which, together with his manner of estimating distances, muft have rendered him liable to many errors. This M. GoSSELIN acknowleges: but he obferves, that he was acquainted with the junction of the Atlantic and Erythrean feas, which Hipparchus and Ptolemy denied; and that he afcertained the length of the Mediterranean, and the fituation of the Ganges, with greater accuracy than fome of the geographers of the last century. In fhort, the author's partiality to this philofopher leads him to magnify his knowlege far beyond the limits of probability, and to confider what, in all likelihood, were only conjectures, as real difcoveries. This appears to be the cafe with the opinion concerning the feas to the fouth of Africa, as Eratofthenes feems to have been entirely ignorant of the extent of that peninfula; and, as to the Ganges, it is evident from what is related of his mode of eftimating diftances, that any coincidence with the difcoveries of modern geographers must have been merely fortuitous.
This partiality to Eratofthenes is very confiftent with an hypothefis which the author maintains: but which admits of no proof, nor, in our opinion, of any prefumption in its favour. He imagines that Pytheas of Marfeilles collected his accounts, not from his own travels, but from ancient traditions and manufcripts, which he altered and difguifed in order to impose them on the world as his own obfervations. This leads M. GOSSELIN to fuppofe that, in a very remote period of antiquity, there exifted a wife and learned nation, which was as well acquainted with the geography of the old world, as we are now: but that this nation was entirely deftroyed, and that the records of its fcience were difperfed, and in a great measure loft, in confequence of events hitherto unknown.
The remainder of this chapter is employed in obfervations on Hipparchus and Polidonius. The former invented the projection
jection of the fphere on a plane furface, and to him may be afcribed the earlieft improvements in aftronomy: but the author fays that geography derived little advantage from his labours, which were fo inaccurate as to render his fyftem still more erroneous than that of Eratofthenes. Pofidonius varied from his predeceffors in this fcience, by allowing only five hundred ftadia to a degree of a great circle, which M. GOSSELIN condemns, as the occafion of many errors with regard to the fituation of places: but the question is, of what value was the ftadium here meant? If this be the Egyptian, which is fuppofed to have been equal to 114 toifes, five hundred will amount to fifty-feven thoufand toifes; which is very near the truth. However, in this author's eftimate, almoft the only merit of Pofidonius as a geographer, confifted in his afferting, in oppofition to Hipparchus, the poffibility of failing round the fouthern extremity of Africa.
In the fecond chapter, M. GOSSELIN animadverts on the fyftem of Strabo. This writer rejected all affiftance from aftronomy and the mathematics, and founded his geography on itinerary diftances, which he collected from his own obfervations, as well as from thofe of others; for his travels furnished him with many particulars unknown to former authors. Like Eratofthenes and Hipparchus, he fuppofed a degree of a great circle to be equal to feven hundred ftadia; and making Rhodes the centre of his obfervations, he estimated the length and breadth of the habitable world, by two lines which he imagined interfected each other at right angles in that place: but he reprefents the whole as a plane furface, admitting no curvatures in the meridians and parallels.
After thefe general obfervations, the author enters into a minute examination of Strabo, pointing out his errors as they occur; this is by far the best part of his work. The chief merit which he afcribes to this geographer, compared with Eratofthenes, is, that he was better acquainted with Gaul and Spain, and lefs inaccurate in fome of his diftances; though, in general, his menfuration is very faulty, and he excels rather in hiftorical, than in geographical knowlege; for to the latter, as founded on aftronomical and mathematical principles, his labours were rather prejudicial than advantageous.
The third part of this differtation contains an examination of the fyftem of Ptolemy, who attempted to establish the science of geography on mathematical principles and aftronomical obfervations. For this purpose, he adopted the mode of projec tion invented by Hipparchus; and he endeavoured to reduce to this plan the longitude of feveral places, which he copied from
Marinus of Tyre: but this reduction, for want of elements fufficient to make it with accuracy, led him into a great number of errors. Among these mistakes, the most important are his making the Mediterranean fea extend twenty degrees too far, and his removing the mouth of the Ganges no less than forty-fix degrees to the eastward of its true pofition. The map of Ptolemy, fays M. GOSSELIN, feems to have been laid down from the fame elements with that of Eratofthenes, but difguifed by a faulty graduation, and rendered erroneous by the computation of five, inftead of feven, hundred ftadia, to a degree.
The maps drawn by M. GOSSELIN, to explain the geogra phical fyftem of Ptolemy, are deduced from a careful examination of feveral manufcript and printed copies of this ancient writer, and differ confiderably from thofe published by Mercator, in the year 1605, which are here cenfured as very inaccurate : but the edition of Bertius, though moft in repute, is, according to our author, the worft; because, befide the mistakes of Mercator, it is full of typographical errors, particularly in the numeral letters.
Among the errors of the ancient geographers, none are more ftriking than thofe which relate to Africa. Strabo imagined that this peninfula did not extend fo far to the south as the equator; and Ptolemy fuppofed that its western coaft was inflected in a fouth-east direction, and continued till it joined that of Afia. In order to account for the great extent which these writers gave to the ifland of Taprobana, M. GosSELIN rejects the common opinion of its being merely Ceylon; and fuppofes that, under this denomination, they included the coaft of Malabar, which they thought was feparated from the continent by, what is now called, the Gulf of Cambaya. He alfo maintains that China was utterly unknown in the age of Ptolemy; and that Siam, which he fays was the country of the Sina, was the extreme limit of the difcoveries of the ancients in that part of the world: but the arguments, by which he endeavours to fupport this hypothefis, are by no means fufficient to convert us to his opinion.
This work is illuftrated by tables of the latitudes and longitudes of places, according to the ancient geographers, compared with those of the moderns, and by eight maps, delineated by M. GOSSELIN, and neatly engraved; of thefe, two relate to the fyftem of Eratofthenes, three to that of Strabo, and five to that of Ptolemy.
ART. XV. Réponse à la Question Phyfique proposée par la Societé de Teyler, &c. i. e. Prize Differtation concerning the Age of our Globe, and the general Revolutions which its Surface has undergone; in Anfwer to a Queftion propofed by Teyler's Philofophical Society. By FRANÇOIS XAVIER BURTIN, Counsellor to the Government of the Netherlands, and Member of feveral Philofophical and Medical Societies. 4to. 390 Pages. Haarlem. 1790.
M. BURTIN introduces himself to his readers with very plaufible profeffions of modefty; acknowleging the narrow limits of human fcience, promifing to reject all hypothetical reasoning, and affuring them that, as he has investigated a multitude of truths, he will make them fubfervient to a moft rigorous demonftration of a general revolution in our globe, much greater, and much more ancient, than the deluge which took place in the days of Noah. Hence we engaged in an attentive perufal of his memoir, with the hope of laying before our readers fuch information as might confiderably facilitate the ftudy of geology; either by the communication of new facts, or by the deduction of new truths from those which had been already obferved; and furely, from the difcuffion of a subject fo interesting, prefaced in a manner fo pompous, and publifhed under the fanction of a very refpectable philofophical fociety, this expectation could not be deemed extravagant: how far it was answered, will appear from a fhort account of the work.
In order, however, to enable our readers to judge of the merits of this differtation, it is proper to lay before them the queftion which M. BURTIN profeffes to anfwer; which is proposed in the following terms: From what is known relative to the nature and fituation of fofils, and the ancient and prefent conftitution of the furface of the globe, how far can we, with certainty, determine what general changes and revolutions it has undergone; and how many ages have elapfed fince thefe took place?
As the foffil kingdom is the foundation on which a theory of the earth must be built, the author devotes his first four chapters to a furvey of that branch of fcience, dividing it, for this purpose, into the two provinces of adventitious and native; the former he fubdivides into animal and vegetable, the latter into primary and fecondary. Under all these feveral heads, he enters into a minute defcription of the various kinds of foffils which he has feen, or of which he has read. We fhall not intrude on the patience of our readers, by following him in
Also called Teyler's Second Society. For an account of its inftitution, fee Review, vol. lxxiii. p. 551.
the course of thefe details, which are very prolix, and, in many particulars, have little connection with the main fubject. They are compiled from various books; among which M. De Luc's Letters on the Theory of the Earth are very frequently quoted; and to thofe who are converfant with this work, they will communicate very little additional knowlege. It is the theory of this philofopher which the prefent author, with no fmall degree of confidence, profeffes to overturn: but he has only thrown it into fuch confufion, as to prevent the reader from having clear and definite ideas, either of the hypothefis which he oppofes, or of that which he means to fubftitute in its ftead.
After the very new and important information, that the word foffil is derived from the Latin verb fodere, M. BURTIN proceeds to convince us, that the fimilarity between our continents and the bottom of the fea, is a proof that the former muft have been, during feveral centuries, covered by the ocean; and that it indicates fome grand revolution, in confequence of which the fea left them dry. However true this may be, M. BURTIN cannot be faid either to have made a new difcovery, or to have adduced new arguments in fupport of one already made. M. De Luc had not only drawn the fame conclufion, but accompanied it with proofs and illuftrations much more clear and fatisfactory than thofe of the prefent author.
When M. BURTIN obferves that, from their thickness, the ftrata of foffil polypes and fhells must have taken a long time to form, that many animal and vegetable foffils there found are now unknown, and that our coals proceed from peat, he advances nothing in which M. De Luc has not anticipated him, with the advantage of much greater perfpicuity of reasoning. He fometimes, indeed, involves the remarks of this gentleman in confufion and obfcurity, by which he gives an air of originality to his own obfervations, and conceals the fource whence they are derived: but when he talks of having demonstrated, that the greatest part of the animals and vegetables, now exifting, are a new generation, totally different from that of which the relics are preferved in the bowels of the earth; that the existence of these, in a foffil ftate, cannot be afcribed to the deluge; we must take the liberty of obferving, that he fubftitutes affertion for proof, and prefumption for demonftration.
M. BURTIN'S obfervations relative to the deluge, are fome of the most vague and unfatisfactory that ever we read: he finds fault with M. De Luc's explanation of this fact, as contradictory of the exprefs words of Mofes, in Genefis vi. 17.