6 A JOURNEY IN BRAZIL. 
carried ou under our government. Mr. Agassiz gave a slight 
sketch of this in opening his lecture. " It was Franklin 
who first systematically observed these facts, though they 
had been noticed long before by navigators. He recorded 
the temperature of the water as he left the .American con- 
tinent for Europe, and found that it continued cold for 
a certain distance, then rose suddenly, and after a given 
time sank again to a lower temperature, though not so low 
as before. With the comprehensive grasp of mind charac- 
teristic of all his scientific results, he went at once beyond 
his facts. He inferred that the warm current, keeping its 
way so steadily through the broad Atlantic, and carrying 
tropical productions to the northern shores of Europe, must 
take its rise in tropical regions, must be heated by a tropical 
sun.* This was his inference : to work it out, to ascertain 
the origin and course of the Gulf Stream, has been, in a 
great degree, the task of the United States Coast Survey, 
under the direction of his descendant, Dr. Bache." f 
* " This stream," he writes, " is probably generated by the great accumu- 
i.ation of water on the eastern coast of America, between the tropics, by the 
trade-winds which constantly blow there." These views, though vaguely 
hinted at by old Spanish navigators, were first distinctly set forth by Frank- 
lin, and, as is stated in a recent printed report of the Coast Survey Explo- 
rations, " they receive confirmation from every discovery which the advance of 
scientific research brings to aid in the solution of the great problem of oceanic 
circulation." 
t No one can read the account of the explorations undertaken by the 
Coast Survey in the Gulf Stream, and continued during a number of successive 
years, and the instructions received by the officers thus employed from the 
Superintendent, Dr. A. D. Bache, without feeling how comprehensive, keen, 
and persevering was the intellect which has long presided over this department 
of our public works. The result is a very thorough survey of the stream, es- 
pecially along the coast of our own continent, with sections giving the temper- 
ature to a great depth, the relations of the cold and warm streaks, the form of 
the ocean bottom, as well as various other details respecting the direction aud 
