xxil INTRODUCTION. 
for many suggestions relating to the history of the discovery of 
the Gulf Stream. 
The commanders of the * Blake," Lieut.-Commander Sigsbee 
and Commander Bartlett, were ever ready to promote the special 
interests of the cruise during my connection with the vessel, and 
they were most cordially supported by the officers and crew in 
this novel work, so foreign to their usual routine. 
In arranging the following sketch of the work of the “ Blake” 
expeditions, I have collected in different chapters what I had to 
say regarding the special subjects of which they treat, based 
upon the experience gained during the voyages with which I 
have been associated. The greater part of these chapters has 
been in type for more than two years; this will account for 
some anachronisms, and for some omissions of reference to pub- 
lieations which would otherwise have been noticed. While of 
eourse dealing with the subject of Thalassography as a whole, 
I have avoided as far as possible all unimportant comparative 
work. 
ALEXANDER AGASSIZ. 
Museum or COMPARATIVE ZOOLocy, 
CAMBRIDGE, December, 1887. 
