TOPOGRAPHY OF THE EASTERN COAST. 101 
admirably shown in the account given by Professor J. E. Hil- 
gard, the Superintendent of the United States Coast Survey, at 
a meeting of the National Academy of Sciences : — 
* We perceive that the basin of the Gulf of Mexico is an oval con- 
nected with the general oczan circulation by two outlets, the Yucatan 
Channel and the Florida Straits. The area of the entire Gulf, cutting 
off by a line from Cape Florida to Havana, is 595,000 square miles. 
Supposing the depth of the Gulf to be reduced by one hundred fathoms, 
a surface would be laid bare amounting to 208,000 square miles, or 
rather more than one third of the whole area. The distance of the 
hundred-fathom line from the coast is about six miles near Cape Flor- 
ida; one hundred and twenty miles along the west coast of Florida; 
at the South Pass of the Mississippi it is only ten miles ; opposite the 
Louisiana and Texas boundary it increases to one hundred and thirty 
miles; at Vera Cruz it is fifteen miles, and the Yucatan Bank has 
about the same width as the Florida Bank. 
“The following table shows the areas covered by the trough of the 
Gulf to the depths stated : — 
Depth. Area. Difference. 
2,000 fathoms. 55,000 square miles. 132,000 
1,500 V 187,000 “ н 73,000 
1,000 Н 260,000  * d 66,000 
500 K 320,000 “ i: 61,000 
100 п 887,000  * d 208,000 
Coast line 595,000 « “ 
“This table shows that the greatest slopes occur between the depths 
of one hundred and fifteen hundred fathoms. The maximum depth 
reached is at the foot of the Yucatan Bank, — 2,119 fathoms. From 
the fifteen-hundred-fathom line on the northern side of the Gulf to the 
deepest water close to Yucatan Dank, — say to the depth of two thou- 
sand fathoms, — the distance is two hundred miles, which gives a slope 
of five-ninths to two hundred, and may be considered practically as a 
plane surface. The large submarine plateau below the depth of twelve 
thousand feet has received the name of the * Sigsbee Deep,’ in honor of 
its discoverer. 
“The Yucatan Channel, with a greatest depth of 1,164 fathoms, has 
a cross-section of one hundred and ten square miles, while the Strait of 
Florida, in its shallowest part opposite Jupiter Inlet, with a depth of 
344 fathoms, has a cross-section of only eleven square miles. 
* A view of the maps reveals at once some important facts, which 
were unsuspected before this great exploration was completed. Thus, 
the distance between the visible coast-lines of the north-eastern point 
