134 THREE CRUISES OF THE “ BLAKE.” 
climate of the arctic regions than it is to-aay, and was felt not 
merely on the coast of Iceland, the Færöes, Norway, Spitzber- 
gen, and along the north shore, of Siberia, but also in the tem- 
perature of Greenland, making it possible for a flora similar to 
that of the temperate zones to flourish there. 
During the tertiary period, the inland sea of Western Asia 
became greatly reduced in extent; and the connection between 
the Indian Ocean and the China Seas, across the central part of 
China and the northern part of India, Arabia, Asia Minor, and 
Palestine, closed the free access of the Indian current from the 
Mediterranean. South America, with the exception of the 
pampas and Amazonian gulfs, had practically assumed its pre- 
sent outline ; while the shore line of the southern part of North 
America had more nearly approached the existing line of the 
Gulf of Mexico. There was thus a less amount of water heaped. 
up in a smaller Gulf of Mexico, and a corresponding decrease 
in the influence of the Gulf Stream of the tertiary period over 
the climate of the arctic region, till in our own epoch the effect 
of this equatorial current is practically felt only on the eastern 
part of the North Atlantic, reaching also toward Nova Zembla 
and the northern shores of Siberia. With the cooling of the 
arctic region a greater influence was exerted by the cold current 
which found its way from the North Pole towards the equator 
along the eastern coast of North America, thus driving the 
warm water towards the eastern part of the North Atlantic 
Ocean. 
The soundings of the “Blake” during the dredging season 
of 1880 developed some striking features in the profile of the 
slope which extends eastward from the shore along the Atlantic 
coast, south of Cape Hatteras as far as the northern extremity 
of Florida. The few lines run in 1880 normal to the coast, and 
the line run parallel to the so-called axis of the Gulf Stream, 
showed the probable existence of an immense submarine pla- 
teau, of which the eastern edge had not been reached, or else 
the soundings indicated a very slight slope from the shore to 
deep water along the whole coast line south of Cape Hatteras to 
the latitude of the Bahamas. 
Everywhere else along the Atlantic coast of the United States 
