Introduction

Eratosthenes was born in Greek colony, Cyrene, in 276 B.C. He got his education at Cyrene and then at Athens. From Athens he was invited by the ruler of Egypt, and appointed chief librarian of the library of Alexandria. This post was considered to be the highest academic honor of the period. He served in the capacity for about 40 years until his death in 194B.C. During his tenure as chief librarian he wrote several scientific and literature books. All her works have unfortunately perished. He attempted  to give the subject of geography a systematic form.

Contribution in geography

• Eratosthenes may be regarded as the first scientific geographer who ascertained the length of the equator with remarkable precision. He also developed the systems of coordinates for the world that is latitude and longitude. He was well acquainted with the astronomical knowledge of the world.

• About the problems of shape, size, position and sphericity of the earth, Eratosthenes adopted the view of the Aristotle and Euclid and regarded the earth as a sphere, placed in the center of the universe, round which the celestial body revolves every 24 hours. 

• He also discovered that the sun and the moon had independent motions of their own. Thus, his idea of the shape of the earth is in conformity with the modern geographer.

• Eratosthenes also tried to measure the circumference of the earth. Apart from his contributions in Astronomy and Geography. He is famous for the correct measurement of the length of the equator with the help of an indigenous apparatus known as Gnomon. Eratosthenes, concluded that the whole world is about 25000 miles in circumference which is near to actual measurement. The only theoretical error in the measurement of the circumference of the earth was that Eratosthenes took the earth as the perfect sphere instead of an oblate spheroid. 

• Eratosthenes also attempted to determine the distance of the Sun and the moon from the earth. He computed the distance of the moon at 78000 miles and that of the sun 400000 miles. There is no account of the process by which he arrived at these conclusions. But these results are far from accurate. He also tried to determine different latitude and longitude. Eratosthenes drew a meridian southward through Alexandria, Syene, Meroe and passing through Rhode, Troade and Byzantium and the mouth of Borethenes on the north shore of black sea. In Spite of shortcoming, Eratosthenes has been called the ‘founder of Geodesy’.

• Regarding Asia he relied on the itineraries of Alexander and his record keepers. He  was also familiar with the fact that the Mt. Taurus was connected with Armenia, Kurdistan and Elburz to the Himalayas. He believed that the Ganges flowed from west to east and merged into the eastern ocean.

• Eratosthenes was well acquainted with the extent and dimension of the Red sea which he described 900 miles from the head of the Gulf to the station of Ptolemais Epitheca. His knowledge about the Nile was superior to that of his predecessors.

• The book written by Eratosthenes describes the ekumene, the inhabited earth in which he accepted both the major divisions of Europe, Asia and Libya and five climatic zones that is a torrid, two temperate and two frigged zones.

• Eratosthenes also tried to determine the spread of the world. According to his calculations, the length of known world from the Atlantic to he Eastern ocean amounted to 2800 miles, while its breadth from the parallel of cinnamon land to that of 3800 miles. He extended the habitable world from Thurles to Taprabone and from Atlantic to Bay of Bengal.