MUSEUM OF COMPARATIVE ZOOLOGY, 59 
due not only to the improvements suggested in the apparatus by Cap- 
tain Sigsbee, by Lieutenants Ackley and Sharrer, and by Messrs. Jacobi 
and Moore, but also to the great care taken by the officer of the deck in 
handling the “Blake ” during the progress of a haul. With a vessel of 
the size of the “ Blake,” excellent judgment was necessary while working 
in a seaway, and that we incurred so few accidents is entirely due to the 
interest taken in the expedition by the officers, and the devices con- 
stantly suggested by them for overcoming the difficulties we encountered. 
in this novel work. 
The accompanying figures (Pl. I.) will explain the modifications intro- 
duced in the dredge and trawl. 
A small map of the Gulf of Mexico, with the 100, 500, 1,000, 1,500, 
1,800, and 2,000 fathom curve, has been prepared at the Coast Survey 
Office in order to give a general sketch of the Hydrography of the Gulf 
of Mexico. Only a small number of the soundings of the “Blake” are 
here introduced; they are selected from an immense number plotted 
during the last four years. The map speaks for itself, and I need only 
call attention in a general way to the principal features of the bottom. 
The most striking characteristics of the Gulf are the two great banks 
extending the one to the west of Florida peninsula and northward of the 
Florida Reef, the other northward of the peninsula of Yucatan, the 100- 
fathom line in both cases running in a general way parallel to the shore 
line and forming the edge of the steep slopes of the deeper parts of the 
central portion of the Gulf of Mexico. The rapidity with which the 
depth increases is very strikingly shown to the north of the Tortugas, and 
to the northward and westward of Alacran Reef, by the proximity of the 
100 and 1,800 fathom curves, the eastern and southern edges of the 
central basin of the Gulf of Mexico having thus very steep sides, while 
the western and northern slopes are far more gradual. The north slope 
off Cuba is also quite abrupt, while the southern slope of the Florida 
Reef into the trough of the Gulf Stream is comparatively gentle. The 
soundings taken in 1878 have developed a remarkable extension of the 
southeast end of the Yucatan Bank within the 1000-fathom curve, in 
the direction of the Tortugas, with a depth of 500 to 700 fathoms for 
over one hundred miles. This will be shown in a more detailed map 
hereafter. 
The greatest depth of the Yucatan Channel is somewhat more than 
1,100 fathoms, so that the temperature of all the water which finds its 
way into the Gulf of Mexico is necessarily at its deepest point (2,119 
fathoms) only the temperature of the bottom of the Straits of Yucatan 
