Oti the Gulf Stream and Currents of the Sea. 171 



Apparently in obedience to the laws here hinted at, there is a 

 constant tendency of polar waters towards the tropics and of tro- 

 pical waters towards the poles. The Exploring Expedition cross- 

 ed one of these hyper-borean currents two hundred miles in 

 breadth at the equator. There is also one near our own coast, 

 another on the west coast of South America, as well as several 

 others elsewhere known to exist ; but for obvious reasons, they 

 are for the most part submarine and but little understood. 



Counter to these are the Gulf Stream and the Lagullus and 

 .Australia currents, besides numerous others more gentle and par- 

 tial, and therefore less marked in their character. But why one 

 of these currents should always run from the Gulf of Mexico, 

 and the other along the coast of Africa and Australia, seems to 

 demand the presence of other agents. Perhaps these may be 

 found in local causes, such as the contour of coasts, the constant 

 force of trade winds, high temperature of the Gulf, &:.c. These 

 would give the first impulse, and may be adequate to the initial 

 velocity of the Gulf Stream. 



Assuming its maximum velocity at five knots, and its depth 

 and breadth in the narrows of Bemini as before, the vertical sec- 

 tion across this stream would present an area of two hundred mil- 

 lions of square feet moving at the rate of seven feet three inches 

 per second. The difference of specific gravity between the vol- 

 ume of gulf water that crosses this sectional line in one second, 

 and an equal volume of water at the ocean temperature of the 

 latitude, is fifteen millions of pounds. If these estimated dimen- 

 sions (assumed here as throughout this paper they have been, from 

 the best authority, but merely for the purposes of illustration) be 

 within limits; then, the force per second operating here to propel 

 the waters of the Gulf towards the pole, is the equilibrating 

 tendency due to fifteen millions of pounds in the latitude of 

 Bemini. 



In drawing up a plan for investigating the currents of the seas, 

 such agencies should be taken into account. As a cause, I doubt 

 whether this one is sufficient of itself to produce a stream of such 

 great and continued velocity as that of the Gulf; for assuming its 

 estimated discharge to be correct, the proposition is almost suscep- 

 tible of mathematical demonstration, that to overcome the resist- 

 ance opposed in cosequence of its velocity, would require a force 

 at least sufficient to drive at the rate of three miles the hour, 



