HOLMES — DISTRIBUTION OF THE HUMAN RACE. 3 



vation of the continent in that part at the close of the Cretaceous 

 period, and secondly, at the close of the Eocene period, by an 

 immense fresh-water lake, covering the region of the great plains 

 to the east of the Rocky Mountains, and extending northwardly 

 from middle Kansas far into British Columbia ; and this lake was 

 still further enlarged, at the close of the Miocene, so as to extend 

 southwardly over the region of Texas and the Gulf of Mexico, 

 making an eftective water barrier to the end of the Pliocene 

 period.* 



Many considerations justify the inference of Mr. Wallace that, 

 at times within the Miocene and Pliocene periods, there was 

 a further extension southwardly than now exists of the conti- 

 nental shores of Asia so as to give a continuous land area from 

 Celebes around to South Africa, including what is now Java, 

 Sumatra, Ceylon, Hindostan, the islands to the northward of the 

 Seychelles, and Madagascar, mostly within the tropical zone; 

 and also, that a like seaward extension of the eastern shores of 

 Asia, in consequence of greater emergence of the land in those 

 times, reached around by Japan and the Aleutian Islands inclu- 

 sive to the North American coast, while warm temperatures still 

 continued in those latitudes. 



These views are further supported by the recent soundings of 

 ocean depths over the globe, by which it appears that an eleva- 

 tion of less than lOO fathoms (30 fathoms, according to Dana and 

 Marsh), in the region of Behring's Straits, would join the two 

 continents by a wide belt of land. And an elevation of 500 to 

 1,000 fathoms would give continuous land from Scotland by the 

 Faroes and Iceland to Greenland, and even to Canada and New 

 England. Eminent botanists, on a comparative study of the plants 

 of Europe and America, and of Spitzbergen and Greenland, have 

 been led to infer, that there must have been some such, land con- 

 nection in Tertiary times, by ineans of which plants native to 

 America found their way into Europe, or were distributed into 

 both America and Europe from the Arctic region. The Miocene 

 flora of Spitzbergen as described by Heer (according to Prof. 

 Oray) has ," two Magnolias, representing, probably, the highest 

 degree of temperature of the Arctic of that epoch, equivalent to 



* Systematic Geology. By Clarence King, U.S. Geologist. 4to, pp, 450-45S. Wash- 

 ington, 1878. 



