Ptolem- ies. R 3111:1115. 176 resulted in a voyage of discgvery from the 11io11tl1 of the : Indus to that of the Tigris, and iii epening direct i11ter- course between Grecian and Iliudu civilization. The Greeks who accompaniel Alexander were accurate ob- servers, and described the towns a11d villages, the products and the aspect of the eouiitry, with care. The con- queror resolved to ret11r11 through Gedrosia (the modern Baluchistaii), but he also i11te11ded to ope11 the trade by sea between Europe and India, and his general 1 Nearchus, anative of Crete, volunteered to lead this famous voyage of discovery. llis fleet consisted of 30 galleys eo1i- I taining 2000 men. 011 October 2, 3:26 15.0., the fleet of Nearchus left the Indus, a11d the anchorages each night are carefully recorded. 011 the 17th of December Cape J ask was doubled a11d the fleet entered the Persian Gulf, and on the 9th of February it was at the mouth of the l{ar1’u1. I Nearchus rejoined Alexander at Susa ; and the conqueror l himself embarked in the fleet and ascended the Tigris to Opi.=, above 13-.1.gl1dad. He then ordered his successful admiral to prepare another expedition for the circumnaviga- tion of Arabia; but unfortunately the great co11q11eror died I at Babylon in 3:24 B.C., and the fleet was dispersed. The dynasties founded by Alexander's generals, Seleucus, Antioehus, and Ptolem_v, encouraged the same spirit of enterprise which their master had so carefully fostered, and extended geographical knowledge in several directions. Seleucus Nicator established the G reeo-Bactrian empire, and continuecl the intercourse with India. The most authentic information respecting the Gangetic valley was supplied by Megasthenes, an ambassador sent by Seleucus, who reached the remote city of Patali-putra, the modern Patna, 011 the Ganges. The Ptolemies of Egypt showed equal anxiety to extend the bounds of geographical knowledge. Ptolemy Euergetes sent an expedition which discovered Abyssinia, and fitted out a fleet under Eudoxus to explore the Arabian Sea. After two successful voyages, Eudoxus left the Egyptian service, and proceeded to Cadiz with the object of fitting - o11t an expedition for the purpose of African discovery ; and we learn from Strabo that the veteran explorer made at least two voyages southward along the coast of Africa. The ' Ptolemies sent fleets annually from their lled Sea ports of Berenice and Myos Hormus to Arabia, as well as to ports 011 the coasts of Africa and India. 4 The Romans did not encourage navigation a11d commerce with the same ardour as their predecessors ; still the luxury of Rome, which gave rise to demands for the varied pro- ducts of -all the eo1111tries of the known world. le:l to an . active trade both by ships a11d caravans. But it was the l military genius of Rome, a11d the ambition for universal empire, which led not only to the discovery but also to the survey of nearly all Europe, a11d of large tracts in Asia and Africa. Every new war produced a new survey and itinerary of the countries which were conquered. In the height of their power the Romans had surveyed and ex- . plored all the coasts of the Mediterranean, Italy, Greece, the Balkan peninsula, Spain, Gaul, western Germany, a11d Britain; but the eastern parts of Germany, Denmark, , Sweden, and Russia. were still unknown regions. In Africa I their empire included Egypt, Carthage, Numidia, and Mauritania. In Asia they held Asia Minor and Syria, had ] sent expeditions into Arabia, a11d were acquainted with the . 111ore distant countries formerly overrun by Alexander, namely, Persia, Scythia, Bactria, and India. Roman inter- course with India especially led to the extension of geo- graphical knowledge. The first Roman who undertook a journey to India was solely influenced by the desire to acquire a knowledge of the people and their doctrines. This was Apollonius, a resident at Antioch, who set o11t towards the close of the (i 1'] 0 (i It A I’ ll Y [l‘lt0(‘-RI-255 or n1.-covisav. first half century of 0111‘ era. He and his attendants, Damis a11d l’hilostratus, reached the I11d11s, andjourneying across the l’unj-ab, came to a bronze pillar with the inscrip- tion “ Ilere Alexander halted ”; b11t it is doubtful whether the party advanced as far the Ganges. It was, however, in the reigns of Severus a11d his inmiediate successors that Jloman intercourse with India was at its height. In all time, while warriors a11d explorers extemled the area of geographical knowledge, there have been students who have striven to systcmatize aml p11t into due form the accumulated i11for1i1atio11. From the first it was perceived that a knowledge of localities could 11ot be attai11ed without so111e 11otio1_1 of their relative positions, and their distances fro111 each other. Consequently the attempts to establish fixed principles 011 which the surface of the earth, or any portion of it, could be delineated, were almost coeval with the earliest voyages of discovery. The first attempt made to determine the position of places appears to have depended on the division of the earth into “climates,”distinguished by the species of a11i111alsa11d plants produced in each. This method, however, was soon aban- ' doned for another, which consisted in observing at places the length of the longest a11d shortest (lays by means of a “gnomon.” An upright pillar of a known height being erected on a level pavement-, by observing the lengths of the meridian shadows the progress of the su11 from tropic to tropic was traced. The 111ost ancient observation with the gnomon is that of Pytheas, in the days of Alex-.n1der the Great, who observed at the summer solstice at llassilia that the length of the meridian shadow was to the height of the g11o111o11 as 213% to 600, a11 observation which makes the ' meridian altitude of the s1111 at Marseilles on that day 70’ 27'. The merit of the invention of the gnomou in Greece is ascribed to the astronomical school of Miletus ; but there is reason to believe that this method of observ-.1tion was invented i11 Egypt, and that Thales carried the knowledge of it into Greece. This was the first step towards co1111ect— ing geography with astronomy; and little further advance was 111ade until the establishment of the famous astrono- mical school of Alexandria. Eratosthenes ('_’7G—l96 1=.c.) was the first who rcduced geography to a regular system, and laid its foundations o11 clear and solid principles. Under the patronage of the Ptolemies he had access to all the materials collected by Alexander and his generals. The doctrine of the splierieity of the earth had by this time been adopted, and the aim of his labours was to delineate, in conformity with this prin- ciple, the known parts of the earth's surface. 1-‘ounding his system on the use of the g11o111on, he supposed a line to be traced through certain places, in all of which the longest day was known to be exactly of the same length. Such a line would evidently be a parallel to the equator. This first: parallel passed through lthodes, a11d was ever afterwards adopted as the basis of ancient maps. Eratosthenes con- tinued his work by tracing other parallels at certain intervals fro111 the first, one through Alexandria, another through Syene, a third through Meroe. He also traced, at right angles to these, a meridian passing through Rhodes and Alexandria, southwards to Syene and Meroe. As the pro- gress which he thus made towards the completion of what he had so skilfully conceived naturally tended to enlarge his ideas concerning geographical science, he attempted next to determine the circumference of the globe by the actual measurement of a segment of one of its great circles. .-tlc1n at syst atizing, ]‘l1‘.'llo- sthene Posidonius made another measurement of an arc of the Posi- meridian between lthodes and Alexandria about 170 years ‘l°"l“3’ afterwards; but the amount of error in the calculations of Eratosthenes and Posidonius is uncertain, for want of a knowledge of the true length of the stadium in which their
results are expressed. The ancients made their first meri-