LESSONS IN GEOGRAPHY. 



SYENE, NOW CALLED ASSOUAN, ON THE NILE. 



ginian admiral, with the thirty thousand persona whom he had 

 on board his vessels, is acknowledged to be authentic ; opinions 

 only differ as to the point where his maritime course terminated. 

 Some will have it that, after having cleared the Pillars of 

 Hercules, he went as far as the Gulf of Guinea, while others 

 limit his exploratory voyage to the month of the Senegal river. 

 Gosselin fixes the limit at Cape Nun. 



Pytheas, a citizen of Marseilles, performed a voyage to the 

 north before the time of Alexander the Great. Ho discovered 

 Albion, or Great Britain, and always sailing in a northern direc- 

 tion, he reached the mysterious place called Ultima Thule, which 

 ho saw covered with ice, enveloped in mist, and, as it were, 

 immersed in a horrible chaos. But what was Thule ? This is 

 a question which has puzzled all historians and geographers. 

 Some have considered with good reason that this country was 

 Jutland or the coasts of Norway called TJiulemark ; or perhaps 

 Iceland, as Pytheas sailed through the Scandinavian seas, and 

 his remarks relating to the coasts of the Baltic have been ac- 

 knowledged exact. Others have claimed this appellation for 

 the Shetland Isles on the north of Scotland. 



Aristotle, the great Greek philosopher and naturalist, main- 

 tained that the earth was of a spherical form, and he even 

 stated the measure of its circumference at 400,000 stadia (a 

 Greek itinerary measure, equal to about 600 feet). Indications 

 of the existence of Madagascar have been noticed in his writings. 

 As to Ceylon, ho mentions it under the name of Taprobane, and 

 that a long time before the age of Ptolemy. The limits of the 

 world according to Aristotle were, on the east, the Indus ; on 

 the west, the Tartessus, or the Guadalquivir ; on the north, the 

 Ripluuan Mountains, Albion, and lerne (Ireland) ; on the south, 

 Libya, in which he places the river Chremetes, which rises out 

 of the same mountains as the Nile, in order to disembogue itself 

 into the Atlantic Ocean an idea which leads to the supposition 

 that ho confounded the Nile with the Niger. He admitted that 

 the Caspian Sea was a great inland lake, having no communica- 

 tion with any other sea. 



The conquests of Alexander the Great led to the most distinct 

 and extended notions of the ancient world. Tho most remark- 

 able geographical fact of his reign was the exploration of the 

 Indus. A fleet of 800 vessels, under the command of * T -vrchns. 



descended this river, and went along the coast of ABU to the 

 bottom of the Persian Gulf. Tho expedition of Alexander opened 

 the eyes of the Greeks, but produced at that time no result* of 

 any consequence to the science of geography. What was gained 

 by his exploratory voyage was lost by the dismemberment of, his 

 empire ; and the historians of the period relapsed into their 

 former ignorance. 



By degrees, however, geography assumed the dignity of 

 science. Eratosthenes, who flourished about 250 B.C., composed 

 a treatise on the subject. He was a native of Cyrene in Africa, 

 and the keeper of the Alexandrian Library. By means of 

 instruments erected in the museum of the city of Alexandria, 

 he found the obliquity of the ecliptic, to within half a degree 

 of the truth. He was the first who attempted to determine the 

 circumference of the earth by the actual measurement of an arc 

 of one of its great circles. By means of sun-dials he found that 

 Syene, near a cataract of the Nile, which was situated, as he 

 thought, on the same meridian as Alexandria, was immediately 

 under the tropic of Cancer, BO that at the time of the summer 

 solstice the sun was vertical to the inhabitants of Syene, and 

 the gnomon had no shadow at noon. Thus, having measured 

 the angle of the shadow of the gnomon at Alexandria, also at 

 the time of the summer solstice, he found the distance of th* 

 sun from the zenith at noon to bo 7 I2f, or one-fiftieth part of 

 the circumference of a great circle, viz., 360. He then com- 

 puted the distance between the two plaoee, Alexandria and 

 Syene, and found it 5,000 stadia. Accordingly, he multiplied 

 this number by 50, and found the measure of the earth's oir- 

 oumference to be 250,000 stadia. Making allowance for the 

 errors which he committed, for want of the delicate instruments 

 of observation which we possess in modern times, this was a 

 tolerable approximation to the truth. Syene, indeed, was not 

 on the same meridian as Alexandria, but on one nearly 3 east 

 of the meridian of that city ; and instead of being exactly on 

 the tropic, it was about half a degree north of that line. Era- 

 tosthones affirmwl tho spherical figure of the earth, and asserted 

 that tho immensity of the ocean would not prevent vessels from 

 poinp to India by continually shaping then- course westward. 



Hipparchus, who flourished about ninety jean later than 

 Eratosthenes, laid the foundation of agtxonomioal geography* 



