TOPOGRAPHY OF THE EASTERN COAST. 101 



admirably shown iii 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 ocean circulation by two outlets, the Yucatan 

 Channel and the Florida Straits. The area of the entire Gulf, cutting 

 off by a line from Cajje 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 folloMdng table shows the areas covered by the trough of the 

 Gulf to the depths stated : — 



" 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 Bank, — 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 



