52 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGT. 



Gulf Stream was sent across the Atlantic in contact with the 

 solid crust of the earth — comparatively a good conductor of heat 

 '—instead of being sent across, as it is, in contact with a cold, 

 non-conducting cushion of cool water to fend it from the bottom, 

 much of its heat would be lost in the first part of the way, and 

 the soft climates of both France and England would be, as that 

 of Labrador, severe in the extreme, ice-bound, and bitterly cold. 



144. Why should the Gulf Stream talce its rise in the Gulf of 

 Mexico ? — That there should be in the North Atlantic Ocean a 

 constant and copious flow and reflow of water between that ocean 

 and the Arctic is (§ 107) not so strange, for there are abundant 

 channel-waj^s between the two oceans. In one, water is to be 

 found nearly at blood heat; in the other, as cold as ice. A 

 familiar experiment shows that if two basins of such water be 

 brought in connection by opening a water-way between them, 

 the warm will immediately commence to flow to the cold, and 

 the cold to seek the place of the warm. But why this warm 

 flow in the Atlantic Ocean should seem to issue from the Gulf 

 of Mexico, as if by pressure, is not so clear. 



145. The trade-winds as a cause of the Gulf Stream. — To satisfy 

 ourselves that the trade-winds have little or nothing to do in 

 causing the Gulf Stream, we may by a process of reasoning, 

 which ignores all the facts and circumstances already adduced, 

 show that they cannot create a current to run when or where 

 they do not blow. The north-east trade-winds of the Atlantic 

 blow between the parallel of 25° and the equator ; the Gulf 

 Stream flows between the parallel of 25° and the Korth Pole. 



146. Gulf Stream impelled by a constantly acting force. — A con- 

 stantly acting power, such as the force of gravitation, is as 

 necessary (§ 95) to keep fluids as it is to keep solids in motion. 

 In either case the projectile force is soon overcome b}^ resistance ; 

 and unless it be renewed, the current in the sea will cease to 

 flow onward, as surely as a cannon-ball will stop its flight 

 through the air when its force is spent. AVlien the waters of 

 Niagara reach Lake Ontario, they are no longer descending an 

 inclined plane ; there, gravity ceases to act as a propelling force, 

 and the stream ceases to flow on, notwithstanding the impulse it 

 derived from the falls and rapids above. A propelling power, 

 having its seat only in the Gulf of Mexico, or the trade-wind 

 region, could (§ 92) no more drive a jet of water across the 

 ocean, than any other single impulse could send any other tra- 



