4 PROCEEDINGS OF THE AMERICAN ACADEMY 



Committee of Publication. 



Joseph Lovering, Jeffries Wyman, 



Francis J. Child. 



Committee on the Library. 



Francis Parkman, Charles Pickering, 



John Bacon. 



Committee to audit the Treasurer's Accounts. 

 Charles E. Ware, Charles J. Sprague. 



Professor Agassiz presented the following communica- 

 tions : — 



I. A report, dated Key West, April 24, from Mr. Henry 

 Mitchell, to Professor B. Peirce, Supt. U. S. Coast Survey. 



1. We have stretched profiles across Nicolas Channel, Santaren Chan- 

 nel, and Gulf Stream from Coffins' Patches to Elbow Key Light. To 

 mention the most interesting item first : we traced a great plateau from 

 Coffins' almost across, and in a central portion of the Straits made rich 

 hauls of coral, living and agglomerated. Mr. Pourtales and myself are 

 satisfied that the reef is growing out there in 200 fathoms of water. 



2. We anchored boat in the axis of the Gulf Stream (as laid down 

 on the Coast Survey chart) and quietly observed the current, — 

 scarcely a mile per hour. 



Our sounding at that point was about 550 fathoms ; no variation of 

 velocity with depth of 75 fathoms. We expected to find an increase 

 not far below the surface, but not an inch was found. We also 

 anchored to the westward of the middle of the Straits, and found 

 greater velocity than in the axis, (so miscalled because warmer.) 



3. Our study of Salt Key Bank and its marginal islands will interest 

 you. 



4. Nicolas and Santaren Channels are motionless masses of water, 

 flat bottom, 300 to 500 fathoms, — very steep banks, say 30° to 40°. 

 The Bahamas and Salt Key Bank are plateaux raised above the level 

 floor of the ocean abruptly. 



5. In the motionless masses of water in Nicolas and Santaren 

 Channels (where we made four current stations at anchor in 300 and 



