THE GULF STEEAM. 379 



the Trade and Anti-Trade Winds will account for many or most of the 

 phenomena of oceanic circulation, that it would be far too discursive for a 

 practical work like this to enter into such a field of speculation. All further 

 theory must be sought for in those works which deal with speculative 

 science. As stated in (2) page 98, the winds and water of the North Atlantic 

 Ocean seem to follow much the same law, as far as their different natures 

 will allow ; that is, they circulate more or less around a central axis or 

 area — the Calms of Cancer in the one case, and the Sargasso Sea in the 

 other. 



Captain Maury adduced arguments against the theory of assuming the 

 Trade Winds as the prime cause of the Gulf Stream, in opposition to the 

 line of reasoning followed by Sir John Herschel. He drew up several 

 Tables to show that the S.E. Trades have a greater preponderating force 

 over the N.E. Trades in the Atlantic, but he proceeds on the assumption 

 of the Equator being the division between the two systems. This basis, 

 which he elsewhere disproved, will very inadequately explain the relative 

 force and duration of the two Trade Winds, as shown in (49), page 129. 

 In fact, from arguing in this way, he endeavoured to prove, that from the 

 much greater force (nearly twice) of the Southern Trades, from their much 

 greater constancy, and still further, that from the greater preponderance of 

 Westerly winds within the Tropics, on the North side of the Equator, that 

 the North-East Trade Wind scarcely hloios at all in the North Atlantic 

 Ocean ; a position which is disproved by his Pilot Charts, and by the ex- 

 perience of all sailors. The statement need scarcely be argued against, that 

 the S.E. Trades have quadruple the force, and nearly double the duration 

 of the N.E. Trades, making them eight times as important. 



But besides this, the Wind and Current Charts demonstrate that the 

 Northern edge of the S.E. Trades, and their consequent drift, are almost 

 always felt throughout nearly the whole year, to the North of the Equator, 

 and, in fact, send a large proportion of the water into the Caribbean Sea 

 (13), page (102). 



The Trade Winds may therefore be held to be a great cause of the Gulf 

 Stream, and this opinion is strengthened by the results of the latest explora- 

 tions made by the United States surveyors.* 



(364.) From careful observations made in the stesbmer Blake, Lieutenant 



• "It is well known how easily a Current may be induced by the action of the Wind, 

 and how a strong S.W., a N.W., or even a N.E. wind, on our own coasts, raises the tide 

 to an extraordinary height in the English Channel, the River Thames, &c., as those 

 winds respectively prevail. The late Mr. Smeaton ascertained, by experiment, that in 

 a canal of 4 miles in length, the water was kept up 4 inches higher at one end than at 

 the other, merely by the action of the wind along the canal. The Baltic is kept up 2 

 feet at least by a strong N.W. wind of any continuance ; and the Caspian Sea is higher, 

 by several feet, at either end, as a strong Northerly or Southerly wind prevails. It is 

 likewise known, that a large piece of water, 10 miles broad, and generally only 3 feet 

 deep, has, by a strong wind, had its waters driven to one side, and sustained so as to 

 become 6 feet deep, while the windward side was laid dry. Therefore, as water pent 

 up so that it cannot escape, acquires a higher level, so, in a place where it can escape, 

 the same operation produces a current, and this current will extend to a greater or less 

 distance, according to the force by which it is produced or kept up by the wind." — 

 Major Reniiell, on the Thicart-Channel Current. , 



