288 J. FE. Hilgard— Basin of the Gulf of Mexico. 
Art. XXXV.—The Basin of the Gulf of Mexico. A communi- 
cation to the National Academy of Sciences made Nov. 18, 
1880, by authority of C. P. Parrerson, Supt. U. S. Coast 
and Geodetic Survey, by J. E. Hitgarp, M.N.A.S. With 
a Map of the Gulf (Plate TX). 
Ar the meeting of the National Academy of Sciences in 
New York, Nov. 18, 1880, Mr. J. E. Hilgard presented, on the 
part of Hon. C. P. Patterson, Superintendent of the U.S. Coast 
and Geodétic Survey, a model of the Gulf of Mexico, con- 
structed from the numerous soundings taken in the progress 
of that work. The accompanying plate (IX) is a reduced plan 
of the model, the full size of which is 24x82 inches, being on 
a horizontal scale of 1: 2,400,000, and on vertical scale of 1 
inch: 1000 fathoms; making the proportion of horizontal to 
vertical scale 1:33. The plan shows the horizontal curves for 
every 500 fathoms of depth, as well as the curveg of 100 and 
10 fathoms. The same curves are delineated on the model, 
the forms of which are shaped in conformity with all the detail 
obtained from the soundings. 
The number of soundings taken within the depth of 100 
fathoms is very large, varying according to the configuration 
and importance of the locality. Beyond 100 fathoms, where 
the work pertains rather to physical exploration than to navi- 
gation, 1,055 soundings have been obtained, which is an 
average of ten to a rectangle comprised within a degree of | 
latitude and longitude ; of these, 355 are in depths greater than 
1000 fathoms. 
The object of this communication being merely to give 4 
general description of the orographic features of the basin of 
this great inland sea—the American Mediterranean—it is only 
necessary to mention here that in connection with the sound- 
ings, temperatures were observed at various depths and the 
organic life was explored by means of dredges. 
of these physical and biological explorations are in the ablest 
hands for discussion and interpretation but are not yet ready 
for publication. It is therefore only necessary to state here, as 
a general fact, that below the depth of about 800 fathoms the 
temperature is everywhere found to be between 39° and 40° 
Before reviewing the structural features of the Gulf-basin- 
which the model reveals in a most striking manner, it is proper 
to recite here briefly the history of the exploration of the 
Gulf by the United States Coast Survey. The surveys of the 
shores and soundings of the approaches were begun as long 
ago as 1846 under the superintendency of Professor A. D. Bache 
and were continued until the outbreak of the Civil War 
25 
ort, as sia Se 
