[41] HISTORY OF THE TILE-FISH. 277" 



remarkable, that similar explorations were continued in 1881, and again 

 during the past season. This year and last Prof. S. P. Baird, the United 

 States Commissioner of Fish and Fisheries, established the headquar- 

 ters of the Commission at Wood's Holl, Mass. This place will here- 

 after be made a permanent station of the Fish Commission. Owing tO' 

 the unusual delay of the Government appropriations our work was de- 

 layed this year about a month in the best part of the season, for we 

 could not begin dredging until August. Unfavorable weather and 

 other causes afterward prevented us from making more than five trips 

 to the Gulf Stream slope this season, but these were very successful. 



"Our dredgings in this region now cover a belt about 160 miles long 

 east and west and about 10 to 25 miles wide. The depths are mostly 

 between 70 and 700 fathoms. The total number of successful hauls 

 made along this belt is now about one hundred and twelve. These 

 have nearly all been made with our large improved trawls; a few have 

 been made with a large rake dredge. At all localities the temperature 

 of the water, both at the bottom and surface, was taken, as well as 

 that of the air. In many cases series of temperatures at various depths 

 were also taken, and other physical observations made and recorded. 

 Lists of the animals from each haul have been made with care and ar- 

 ranged in tables. In this region the bottom slopes very gradually from 

 the shore to near the 100-fathom line, which is situated from 80 to 100 

 miles from the mainland. This broad, shallow belt forms, therefore, a 

 nearly level plateau with a gentle slope seaward. Beyond the 100- 

 fathom line the bottom descends rapidly to more than 1,200 fathoms 

 into the great ocean basin, thus forming a rai)idly sloping bank as steep 

 as the side of a mountain and about as high as Mount Washington, 

 New Hampshire. This we call the "Gulf Stream slope," because it de- 

 termines practically the inner border of the Gulf Stream all along our 

 coast from Cape Hatteras to Nova Scotia. In our explorations a change 

 of locality of less than 10 miles would often make a difference of more 

 than 3,500 feet in depth on this slope. The upper part of the slope and 

 the outermost portion of the adjacent plateau, in 65 to 150 fathoms, is 

 bathed by the waters of the Gulf Stream, and consequently the tem- 

 perature of the bottom water along this portion is decidedly higher 

 than it is along the shallower part of the plateau nearer the shore. 

 Moreover, the Gulf Stream itself is limited in depth to about 150 fath- 

 oms or often less, and below this the temperature steadily decreases to 

 the bottom of the ocean basin. We may therefore properly call the 

 upper part of the slope in 65 to 150 fathoms the " warm belt." Our ob- 

 servations give the bottom temperature of this warm belt as usually 

 between 48° and 50° Fahrenheit. On this belt we took numerous kinds 

 of animals that were previously known only from the Gulf of Mexico 

 or off Florida. Some of them belong to tribes that have always been 

 cousideied as tropical, or subtropical, such as Dolium, Marginella, and 

 Avicula among the shells. In fact this belt is occupied by a northern 



