One of his first endeavours was, to verify the obliquity of the ecliptic, as settled by Eratosthenes: he next fixed, as accurately as possible, the latitude of Alexandria; but it would lead us far from the object of our work, if we were even briefly to mention his discoveries in the science of pure astronomy. We must confine ourselves to those parts of his discoveries which benefitted geography, either directly or indirectly. After having, as successfully as his means and the state of the science would permit him to do, fixed the position of the stars, he transferred the method which he had employed for this purpose to geography: he was the first who determined the situation of places on the earth, by their latitudes and longitudes, with any thing like accuracy. The latitude, indeed, of many places had been fixed before; and the means of doing it were sufficiently simple and obvious: but with respect to some general and safe mode of ascertaining the longitudes, the ancient philosophers before Hipparchus, were ignorant of it. He employed for this purpose the eclipses of the moon. After having ascertained the latitudes and longitudes of a great many places, he proposed to draw up a catalogue of terrestial latitudes and longitudes, but this he was not able to accomplish: he had set the example, however and it was followed by subsequent astronomers. He fixed on the Fortunate Islands, which are supposed to be the Canaries, for his first meridian. His principal works most probably were destroyed in the conflagration of the Alexandrian library. His catalogue of the stars is preserved in the Almagest of Ptolemy; and his commentary on Aratus and Eudoxus is still extant.
Such is a brief sketch of the advantages which geography, as founded on astronomy, derived from the labours of Hipparchus. We possess little information respecting his ideas of the form of the earth, or the relative position or extent of the different quarters and countries on the surface of the globe. He seems to have been the first who conceived the idea of a southern continent, uniting Africa and India: he had evidently some information, though very vague and erroneous, of India, beyond the Ganges. On the east coast of Africa, his knowledge did not extend beyond Cape Guardaferi. On the whole, geography is more indebted to him for his discoveries in astronomy, and, above all, for his setting the example of carefully ascertaining facts, and not indulging, so much as his predecessors had done, in conjectures and hypotheses, than for any actual discoveries or advances he made in it. The eulogium which Pliny has pronounced on him is very eloquent, and fully deserved. "Hipparchus can scarcely receive too high praise: he has proved, more satisfactorily than any other philosopher, that man is allied to heaven, and his soul derived from on high. In his time, more than one new star was discovered, or rather appeared for the first time; and this induced him to believe, that future ages might witness stars for the first time moving from the immense regions of space, within the limits of our observation. But the grandeur and boldness of Hipparchus's mind rested not here: he attempted, and in some measure succeeded in doing, what seems above human knowledge and power: he numbered the stars, laid down rules by which their rising and setting might be ascertained beforehand; and, finally, he constructed an apparatus on which the position of each star was accurately given, and a miniature picture of the heavens, with the motions of the celestial bodies, their rising and setting, increase and diminution. He thus may be said to have left the heavens as a legacy to that man, if any such were to be found, who could rival him and follow his steps."
From the time of Hipparchus to that of Ptolemy the geographer, the Alexandrian school, though rich in philosophers, who devoted their studies and labour to other branches of physical and metaphysical science, did not produce one, who improved geography, or the sciences on which it depends, with the exception of Posidonius. This philosopher, who belonged to the sect of the Stoics, was born at Apamea in Syria: he usually resided at Rhodes, and was the friend of Pompey and Cicero. The former, on his return from Syria, came thither to attend his lectures. Arriving at his house, he forbad his lictor to knock, as was usual, at the door; and paid homage to philosophy, by lowering the fasces at the abode of Posidonius. Pompey, being informed that he was at that time ill of the gout, visited him in his confinement, and expressed himself very much disappointed that he could not have the benefit of his lectures. Posidonius, thus honoured and flattered, in spite of his pain, delivered a lecture in the presence of his noble visitor; the subject of which was to prove, that nothing is good which is not honourable. Cicero informs us, that he also attended his lectures; and according to Suidas Marcellus, brought him to Rome in the year of the city 702; in this, however, Suidas is not supported by other and contemporary writers.
We are indebted to Cleomedes for most of what we know of his opinions and discoveries; with such as relate to morals or to pure astronomy, we have no concern. But he was of service also to geography. He measured an arc of the terrestrial meridian; but his operation, as far as we can judge by the details which have reached us, was far from exact, and of course his result could not be accurate; it would appear, however, that his object was rather to verify the ancient measures of the earth, particularly that of Eratosthenes, and that he found them to agree nearly with his own. He explained the ebbing and flowing of the sea, from the motion of the moon, and seems to have been the first who observed the law of this phenomenon. In order to represent the appearance of the heavens, Cicero informs us that he constructed a kind of planetarium, by means of which he exhibited the apparent motion of the sun, moon, and planets round the earth. It is on the authority of Posidonius, that Strabo relates the voyage of Eudoxus of Cyzicum from the Persian Gulf round Africa to Cadiz, which we have already mentioned.
Having thus exhibited a view of the discoveries in geography, the advances in the sciences connected with it, and the commercial enterprises of the Egyptians, while under the dominion of the Ptolemies, it will be proper, before beginning an account of the geographical knowledge and commercial enterprises of the Romans (who, by their conquest of Egypt, may be said to have absorbed all the geographical knowledge, as well as all the commerce of the world, at that period), to recapitulate the extent of the Egyptian geography and commerce, especially towards the east We shall direct our retrospect to this quarter, because the commodities of the east being most prized, it was the grand object of the sovereigns and merchants of Egypt, to extend and facilitate the intercourse with that quarter of the globe as much as possible. And we are induced to undertake the retrospect, because the exact limit of the geographical knowledge and commercial enterprise of the Ptolemies is differently fixed by different authors: some maintaining that the Egyptians had a regular and extensive trade directly with India, and of course, were well acquainted with the seas and coasts beyond the Red Sea; while other authors maintain, that they never passed the straits of Babelmandeb, and that even within the straits, their geographical knowledge and commercial enterprises were very limited.
It cannot be doubted that commerce and the spirit of discovery flourished with more vigour, and pushed themselves to a greater distance in the reigns of Ptolemy Philadelphus, and Ptolemy Euergetes, than in the reign of any of their successors. If, therefore, there are no proofs or traces of a direct and regular trade with India in their time, we may safely conclude it did not exist in Egypt, previously to the conquest of that country by the Romans.
We are well aware, that there are great authorities opposed to the opinion which we hold; but these authorities are modern; they are not, we think, supported by the ancient writers, and in opposition to them, we can place the authority of Dr. Vincent, a name of the very greatest weight in questions of this nature. The authorities we alluded to in support of the opinion, that there was a direct trade with India under the Ptolemies, are Huet, in his History of the Commerce and Navigation of the Ancients; Dr. Robertson, in his Disquisition on India, and Harris, or perhaps, more properly speaking, Dr. Campbell, in his edition of Harris's Collection of Voyages and Travels. Huet, as is justly remarked by Dr. Vincent, drops the prosecution of the question at the very point he ought to introduce it; and afterwards countenances, or seems to countenance, the opposite opinion. Dr. Robertson bestows much labour, ingenuity, and learning in support of the opinion, that under the Ptolemies, a direct trade was carried on with India; yet, after all, he concludes in this manner: "it is probable that their voyages were circumscribed within very narrow limits, and that under the Ptolemies no considerable progress was made in the discovery of India:" and when he comes to the discovery of the Monsoon by Hippalus and the consequent advantage taken of it to trade directly to India, by sailing from shore to shore, he acknowledges that all proofs of a more early existence of such a trade are wanting. Dr. Campbell virtually gives up his support of the opinion, that a direct trade was carried on under the Ptolemies, in the same manner.
We have already remarked, that the strongest spirit of enterprize that distinguished Egypt existed in the reign of Ptolemy Philadelphus and Ptolemy Euergetes; that these monarchs pushed their discoveries, and extended their commercial connections much farther than any of their predecessors; and that therefore, if a direct and regular communication between Egypt and India did not take place in their reigns, we may be assured it was unknown to the Egyptians at the period of the Roman conquest. To their reigns, then, we shall principally direct our enquiries.
That Ptolemy Philadelphus was extremely desirous to improve the navigation of the Red Sea, is evident from his having built Myos Hormos, or rather improved it, because it was more convenient than Arsinoe, on account of the difficulty of navigating the western extremity of that sea: he afterwards fixed on Berenice in preference to Myos Hormos, when the navigation and commerce on this sea was extended and improved, since Berenice being lower down, the navigation towards the straits was shorter, as well as attended with fewer difficulties and dangers. But there is no evidence that his fleets, which sailed from Berenice, were destined for India, or even passed the Straits of Babelmandeb. It is, however, not meant to be asserted that no vessels passed these straits in the time of this Ptolemy. On the contrary, we know that his admiral, Timosthenes, passed the straits as low as Cerne, which is generally supposed to be Madagascar; but commerce, which in our times, directed by much superior skill and knowledge, as well as stimulated by a stronger spirit of enterprize and rivalship, and a more absorbing love of gain, immediately follows in the track of discovery, was then comparatively slow, languid, and timid as well as ignorant; so that it is not surprizing that it did not follow the track of Timosthenes. Ptolemy Philadelphus also pushed his discoveries by land as far as Meroc: he opened the route between Coptus and Berenice, establishing ports and opening wells; and from these and other circumstances he seems to have been actuated by a stronger wish to extend commerce, and to have formed more plans for this purpose, than any of his successors.
Ptolemy Euergetes directed his thoughts more to conquest than to commerce, though he rendered the former, in some degree, useful and subservient to the latter. After having passed the Nile, and subdued the nations which lay on the confines of Egypt, he compelled them to open a road of communication between their country and Egypt. The frankincense country was the next object of his ambition: this he subdued; and having sent a fleet and army across the Red Sea into Arabia, he compelled the inhabitants of the district to maintain the roads free from robbers, and the sea from pirates--a proof that these people had made some advances in seafaring matters, and also of the attention paid by Euergetes to the navigation of the Red Sea, as well as to the protection of land commerce. Indeed the whole of his progress to Aduli, which we have more particularly mentioned in another place, was marked as much by attention to commerce as by the love of conquest; but though by this enterprize he rendered both the coasts of the Red Sea tributary, and thus better adapted to commerce, there is no proof that he passed the Straits of Babelmandeb. It is true, indeed, that he visited Mosullon, which lies beyond the straits, but not by sea, having marched by land to that place, through the interior of Abyssinia and Adel. From the whole of this enterprize of Euergetes we may justly infer, that though he facilitated the intercourse by land between Egypt and those parts of Africa which lay immediately beyond the straits, yet his ships did not pass the straits, and that in his reign the discoveries of Timosthenes had not been followed up or improved for the purpose of trading by sea with the coast of Africa. The navigation of the whole of the Red Sea, at least on the Arabian side, from Leuake Kome to Sabaea, was undoubtedly known and frequently used at this period; but this was its utmost limit.