IV. 
TOPOGRAPHY OF THE EASTERN COAST OF THE NORTH AMERICAN 
CONTINENT. 
OnLy the most general features of the topography of the 
Western Atlantic, including the Gulf of Mexico and the Ca- 
ribbean, were known before the explorations of the “ Blake.” 
The course of the hundred-fathom line from George’s Bank to 
Cape Hatteras, the Straits of Florida and the Gulf of Mexico, 
was accurately laid down from the work of the hydrographic 
parties of the United States Coast Survey. (Fig. 55.) The 
hundred-fathom line indicates in a general way the true conti- 
nental outline of the eastern coast of the United States. The 
continental slope connecting this submarine shelf with the bed 
of the Atlantic, and with the basins of the Gulf of Mexico and 
of the Caribbean, was traced in its details by the successive ex- 
peditions of the “Blake.” We must except the oceanic lines 
run by the “Challenger,” connecting Nova Scotia and New 
York with the Bermudas, and the Bermudas with St. Thomas." 
1 «Similar investigations,” says Pro- 
fessor Hilgard in an account of the work 
of the * Blake," “have since been pros- 
ecuted by Commanders Bartlett and 
Brownson, U. S. N., under the direction 
of the Superintendents of the Coast Sur- 
vey, in the western part of the North At- 
lantic, — that great embayment, which, 
limited by Newfoundland on the north 
and by the Windward Islands on the 
south, might be not inaptly named the 
Gulf of North America. The depths and 
temperatures obtained by these officers, 
upon lines run aeross the course of the 
Gulf Stream, and connecting with those 
run by H. M. S. *Challenger? in 1873, 
will make apparent the part taken by the 
Coast Survey in developing the configu- 
ration of the ocean-bed between the Ber- 
mudas and the West India Islands, and 
northward to the Banks of Newfound- 
land, and in defining the limits of the 
continental plateau, which, extending 
from the coast to the hundred-fathom 
line, may be described as the western rim 
of this great basin of the North Atlantie. 
. .. During the winter of 1881 to 1882 
the ‘Blake’ was engaged in developing 
the limit and general character of the 
great Atlantie basiu between the Bermu- 
das and the Bahamas, and along the out- 
side of the West India Islands as far to 
the eastward as St. Thomas. "This eruise 
has been of great interest. 'The bed of 
