178 The American Naturalist. 



;m,- 



through the Straits of Babelmandeb into the Indian Ocean, 

 bringing home the produce of the tropical regions ; while the 

 ships sent westward to the Atlantic returned with tin, silver, 

 lead and other metalic products of Spain and Great Britian. 



The earliest idea formed of the earth seems to have been 

 that it was a flat circular disk, surrounded on all sides by 

 water, and covered with the heavens as with a canopy, even 

 philosophers looked upon the earth as a disk swimming upon 

 the water. Homer (800 B. C.) regarded the earth as a flat cir- 

 cle surrounded by mysterious waters. The nations that were 

 upon its border were called Cimmerians, and were supposed to 

 live in perpetual darkness. 



As the ancients slowly gained a knowledge of the country 

 surrounding their provinces through commercial intercourse, 

 wars, and the search for knowledge, they were undoubtedly 

 struck with the differences of the topography and formations. 

 Thus geology is undoubtedly the outgrowth of geographical 

 knowledge. 



The 7th and 6th centuries B. C. were remarkable for great 

 advance in the knowledge of the form and extent of the earth. 



Their first discoveries were probably made by the Phoeni- 

 cians. Their investigations were along the shores of the Med- 

 iterranean, and passing through the. Straits of Gibraltar, they 

 extended their researches into Spain and Africa and the Can- 

 aries. 



Pythagoras (583 B. C.) observed the phenomena that were 

 then attending the surface of the earth, and proposed theories 

 for explaining the changes that had taken place in geological 

 time. He held that in addition to volcanic action, the changes 

 in the level of the sea and land were due to the retiring of the 

 sea. 



Aristotle (384 B. C.) recognized the interchange constantly 

 taking place between land and sea by the action of running 

 water and of earthquakes, and remarked " how little man can 

 perceive in the short space of his life of operations extending 

 through eternity of time." 



Geographical knowledge was greatly advanced by the con- 

 quest of Alexander the Great (356 B. C), in making known 



