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POPULAR SCIENCE MONTHLY. 



that there is no room for the Terra Australis of classical and mediaeval 

 cartographers. Nevertheless he was convinced that there was a nucleus 

 of land in the middle of the ice-pestered sea, for he accepted the view 

 that thick ice is not formed on the open sea. This view was based on 

 the argument advanced by de Brosses in 1756, that as sea ice is sweet 

 it must be formed on land, until in 1776 Nairsie explained that ice 

 formed by the freezing of the sea water is fresh because the salt is ex- 

 truded as brine. Cook, however, was no doubt quite correct in the view 

 that the great fiat-topped Antarctic bergs could not be formed by the 

 direct freezing of the open sea, but must have been formed on land. 



TeERA AUSTltALIS (Tiieatkum Geeis Terkarum, 1571). 



Mar DEL 



Terra Austealis, after Mercator (Atlas Minor, ex-officina Joannis Janssonii, 164:*). 



Hence in spite of the comparatively narrow limits within which 

 Cook's work had restricted the possible existence of Antarctic land, the 

 search for it was still continued. Islands were found south of the 

 Atlantic; but it was not till 1840 that any extensive land area was dis- 

 covered south of the Pacific and Indian Oceans. Then almost simul- 

 taneously a French expedition under Dumont d'Urville, and the Amer- 

 ican expedition under Wilkes discovered the long coast line or chain of 

 islands known as Wilkes Land. 



Wilkes' work was not only important because he traced this coast 

 line at intervals for 60 degrees of longitude; but the geological collec- 

 tions made by his expedition showed that the land is formed of 

 granites, massive sandstones and other rocks of continental types. 



Two years later the extension of Wilkes Land to the east and the 

 south was proved by the famous expedition of Sir James Clark Ross, 

 which circumnavigated the Antarctic area and passed all previous 



