102 THREE CRUISES OF THE " BLAKE." 



of Yucatan and the west coast of the Florida peninsula is four hundred 

 and sixty miles, while the distance between the submerged contours of 

 five hundred fathoms is only one hundred and ninety miles ; between 

 the contours of one thousand fathoms only ninety miles. These facts 

 at once characterize the Gulf of Mexico as a Mediterranean Sea. 



" The most striking features displayed by the map are : — 



"The great distance to which the general slope of the continent 

 extends below the present sea-level before steeper slopes are reached. 

 The hundred-fathom curve represents very closely the general conti- 

 nental line ; the massifs of the peninsulas of Florida and Yucatan 

 have more than twice their present apparent width. 



" Very steep slopes lead from this submerged plateau to an area of 

 fifty-five thousand square miles, — as great as that of the State of 

 Georgia, — at the great depth of over twelve thousand feet. There 

 are three ranges on the Florida and Yucatan slopes, extending in the 

 aggregate to more than six hundred miles, along which the descent 

 between five hundred to fifteen hundred fathoms, or six thousand feet, 

 is within a breadth of from six to fifteen miles. No such steep slopes 

 and correspondingly elevated plateaux appear to exist on the unsub- 

 merged surface of the earth. With the exception of the deep sub- 

 marine valleys, canons, and steep slopes found in the proximity of 

 volcanic islands, continental slopes are small, except beyond the conti- 

 nental shelf, as off the Yucatan and Florida plateaux at the Bermudas, 

 Bahamas, and off Hatteras. 



" The protrusion of the Mississippi delta toward the deep water of 

 the Gulf seems to give evidence to the engineer of the probably per- 

 manent success of the Mississippi jetties, as delivering the silt of the 

 river into water of so great depth, that but few extensions will ever 

 become necessary." 



The principal topographical features of the Gulf of Mexico 

 are the great banks which lie within the hundred-fathom line, 

 and occupy no less than one-third of the surface. While the 

 shore line of Texas and Louisiana slopes very gTadually towards 

 the deepest part of the Gulf (Sigsbee Deep), the Mexican coast- 

 line north of Vera Cruz is somewhat steejjer. The west slope 

 of the great Florida Bank as well as the north-west slope of the 

 Yucatan Bank are characterized by their steep inclinations. In 

 two places along the Yucatan Bank the horizontal distance be- 

 tween the hundred-fathom line and the fifteen-hundred-fathom 

 curve is only from fifteen to twenty miles. 



If now we attempt to get a general idea of the submarine 



