THE GULF STREAM. 249 



ered by Mr. Hilgard as an immense hydrostatic reservoir, rising 

 to the height of more than three feet ^ above the general oceanic 

 level, and from this supply comes the Gulf Stream, which passes 

 out through the Straits of Bemini, the only opening left for its 

 exit. 



Arago, Lenz, and Leonardo da Vinci before them, maintained 

 that since the water of the equator was greatly heated and 

 lighter, and attained a higher level, there was a flow of the sur- 

 face waters towards the poles, a compensation being established 

 by the flow of lower strata from the poles to the equator. The 

 principal features of this thermic theory have of late found their 

 most efficient exponent in Dr. Carpenter. The results of his 

 experiments to prove this theory upon a small scale seemed to 

 show that the cooling of the waters at the pole, and their rapid 

 fall, were a more efficient force than the heating of the water at 

 the equator. Ferrell has caUed attention to the phenomenon 

 that cold water at the bottom will be swung more to the west- 

 ward than the water at the top, which will be turned in an east- 

 erly direction. As the particles of water ascend, they retain the 

 velocity they had in deeper parts of the ocean, and thus, when 

 reaching either the surface or lesser depths than their original 

 position, they must show themselves as producing a westerly 

 current. This current, deflected by the continental masses as 

 it strikes the east coast, would then be set in motion towards 

 either the north or s6uth pole. At the equator, the water 

 which flows westward from the eastern shores of the continen- 

 tal masses can only be replaced by the compensating waters 

 flowing to it from the north and south. This circulation fairly 

 agrees with the phenomena observed in the South and North 

 Atlantic. 



It is interesting to trace the gradual development of our 

 knowledge of the Gulf Stream, and to see how far-reaching 

 has been the influence of the oceanic currents upon the explora- 

 tions of maritime nations, and the effect these have had in their 



^ By a most careful series of levels, first point is forty inches lower than the 



run from Sandy Hook and the mouth of Gulf of Mexico at the mouth of the Mis- 



the Mississippi River to St. Louis, it was sissippi. 

 discovered that the Atlantic Ocean at the 



