172 On the Gulf Stream and Currents of the Sea. 



ninety thousand millions of tons up an inclined plane, having an 

 ascent of three inches to the mile * 



Yet the very principle from which this motive power is derived, 

 is admitted to be one of the chief causes of those winds which 

 are said to be the sole cause of this current. 



But in addition to this, may there not be a peculiar system of 

 laws, not yet fully understood, by which the motion of fluids in 

 such large bodies is governed when moving through each other 

 in currents of different temperature ? That currents of sea wa- 

 ter having different temperatures do not readily commingle, is 

 shown by the fact already metioned, that the line of seperation 

 between the warm waters of the Gulf and the cold waters of the 

 Atlantic is perfectly distinct to the eye for several hundred miles; 

 and to the thermometer even at the distance of one thousand miles, 

 though the two waters have been in constant contact and continu- 

 ed agitation for many days, the thermometer shows that the cold 

 water on either side still performs the part of river banks in keep- 

 ing the warm waters of the stream in their proper channel. 



In a winter's day off Hatteras, there is a difference between 

 these waters of 20° .f Those of the Gulf being warmer, we are 

 taught to believe they are also lighter ; they should therefore oc- 

 cupy a higher level than those in which they float. Assuming 



ft 



iddle 



lowing the usual rate of expansion, figures show that the mi 

 of the Gulf Stream here, should be nearly two feet higher than 

 the contiguous waters of the Atlantic. Were this the case, the 

 surface of the stream would present a double inclined plane, from 

 which the water would be running down on either side as from 

 the roof of a house. As this ran off at the top, the same weigh* 

 of colder water would run in at the bottom ; and thus, before this 

 mighty stream had completed half its course, its depth would he 

 brought up to the surface, and its waters spread out over the ocean. 

 Why then does not such a body of warm water, flowing and a - 

 hering together through a cold sea, obey this law and occupy 

 higher level ? That it does not, we may infer from the silence 

 of navigators on the subject, as well as from other circumstances' 

 If it did, the upper edges of its cold banks would support a latera 





* Without friction. 



t Off the Grand Banks there is sometimes a differcuce of 30°. 



