THREE CRUISES OF THE BLAKE 185 



it was possible to strain a column of water of any height 

 desired, at any given depth. A considerable number of 

 experiments with this apparatus resulted in their being 

 unable to find any life below one hundred fathoms. 

 These investigations led Agassiz to believe that between 

 the fauna living at or comparatively near the surface, 

 and the animals living close to or on the bottom, there 

 was a vast belt of water where practically no life existed. 



This theory Agassiz maintained to the end of his life, 

 in opposition to many naturalists, although from his 

 later investigations in other parts of the world he came 

 to the conclusion that the upper zone of life was con- 

 siderably thicker than he had at first supposed. This 

 question will be referred to again at greater length in a 

 subsequent chapter. 



By an arrangement with Sir Wyville Thomson, the 

 collections of the first two cruises of the Blake were sent 

 to the same specialists who had undertaken the study 

 of the material gathered by the Challenger. But much 

 of the plunder dredged on the third cruise was given to 

 the naturalists who were working on the collections 

 gathered along the Atlantic seaboard by the Fish Com- 

 mission. 



During these voyages Agassiz was able to add ma- 

 terially to our knowledge of the warm current, which 

 forces its way between the Straits of Florida and, separ- 

 ated from the coast of America by a cold arctic stream, 

 flows in a northeasterly direction and bathes the coasts 

 of northwestern Europe. Benjamin Franklin appears to 

 have made the first real study of the Gulf Stream, of 

 which he published a chart for the aid of navigators, 

 based on information obtained from Nantucket whale- 

 men. Humboldt and Arago are among those who have 



