No. 6. — (LETTER No. 2) To C. P. PATTERSON, Superintendent Coast 
Survey, Washington, D. C., from ALEXANDER AGASSIZ, on the 
Dredging Operations of the United States Coast Survey Steamer 
* Blake,” during parts of March and April, 18'78, with the Prelimi- 
nary Report on the Mollusca of the Expedition, by Wm. 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 Orleans 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 Dank, 
in lat. 26° 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. 
