No. 6. — (Letter No. 2) To C. P. Patterson, SuperintcTident Coast 

 Survey, Washington, D. C, from Alexander Agassiz, on the 

 Dredging Operations of the United States Coast Survey Steamer 

 " Blake" during jiarts of March and April, 1878, ivith the Prelimi- 

 , nary Bcjjort on the Mollusca of tlie Expedition, ty "VVm. H. Dall, 

 Assist. U. S. Coast Survey. 



Since my last letter our operations have been confined to dredgings 

 along a line to the northward of the Tortugas, running, in a general 

 way, parallel to the 100-fathom curve of the western edge of the great 

 Florida Bank. This line was extended northward to about the latitude 

 of Tampa Bay, a distance of some 200 miles. A second line was then 

 run from that point directly for the mouth of the Mississippi, a distance 

 somewhat less than 200 miles. At New Oi-leans Mr. Garman and 

 myself left the ship. It must have been a great relief to the officers 

 of the " Blake," more particularly to the executive officer, Lieutenant 

 Ackley, to be able to put the " Blake " again in an orderly condition. 

 The work of dredging is not conducive to cleanliness, and during the 

 whole time I was on board no routine was ever allowed to interfere 

 with our work. Lieutenant Ackley himself always being the first to see 

 that everything was in readiness for our dredging operations at all 

 times. That the interest shown in the work by the other officers of 

 the " Blake," Messrs. Sharrer, Jacobi, Moore, Sigsbee, and Dr. Nourse, 

 did not flag after my departure, is amply testified by the collections 

 made off Havana, containing some of the most valuable specimens of 

 the expedition, all of which were forwarded to the Museum in an ex- 

 cellent state of preservation. The " Blake " subsequently returned to 

 Key West to continue her regular work of sounding between the Tortu- 

 gas, the coast of Cuba, and the Yucatan Bank. On the way to Key 

 West, a few casts were made by Captain Sigsbee, on the Florida Bank, 

 in lat. 2G° 31', long. 89° 03', in a depth of 119 fathoms, at a point 

 where a good idea of the fauna of the Florida Bank could be obtained. 

 Before setting ashore the dredging apparatus. Captain Sigsbee ran over 

 to Havana, hoping to be able to dredge a few specimens of Pentacri- 

 nus in one of the localities where we had, on a former occasion, found 

 innumerable fragments of stems. He was most successful in this at- 



