PHILOSOPHICAL SOCIETY OF WASHINGTON. 53 



exploration with great energy and ingenuity, has brought the work 

 to a speedy conclusion. 



As a result of these investigations, it is found that the continental 

 profiles which descend from every direction beneath the water of 

 the gulf, have, at first, a very gradual slope of a few feet to the 

 mile — until the 100 fathom depth, or thereabout, is reached. They 

 then descend much more rapidly, and, in some places, with singular 

 abruptness to depths exceeding 2,000 fathoms. All around the gulf 

 shores is a marginal belt of varying width and of comparatively 

 shallow water. Within this marginal belt is an area of similar 

 shape to that of the gulf itself, and nearly concentric with its coast, 

 where the depth is comparable to that of mid-ocean. The extent of 

 the deeper area is about 50,000 square miles. It also appears that 

 the continental or peninsular mass of Florida is of much greater area 

 than that portion which exposes its surface above the water, and the 

 same is true of Yucatan. An examination of the portions in the 

 vicinity of the Mississippi river, shows that the delta has very nearly 

 reached the position where the profile begins to drop rapidly down 

 into deep water, and the apprehensions of those who fear that the 

 jetties lately constructed may cause the accumulation of deposits 

 further out may therefore be dispelled or greatly mitigated. 



Turning to the channel of the Gulf stream, Mr. Hilgard remarked 

 that its transverse section between Florida and the Bahama Banks, 

 did not exceed twelve square miles. With an average current 

 velocity of only 2 i miles per hour, it appears quite incredible that 

 enough water can be dischaged through this passage to occasion the 

 mild climate of western Europe. The main mass of the great 

 oceanic drift which warms these shores, he thought must be derived 

 from the Caribbean Sea, passing out between the greater Antilles, 

 where the passes are far wider and deeper. Of this greater oceanic 

 drift the efflux through the Florida straits forms but a small part. 



Remarks upon this communication were made by Messrs. Alvord, 

 Dutton, Gill, Harkness and White. 



The Society then adjourned. 



190th Meeting. December 18, 1880. 



The President in the Chair. 

 Forty-two members present. 

 The minutes of the last meeting were read and adopted. 



