THE GULF STREAM. ZO 



of water from tlie shores of America to the shores of Europe, that 

 exceeds in discharge the mighty Mississippi a thousand times ? 

 Eeason teaches and examination shows that they are nc^t. AVith 

 the view of ascertaining the average number of days during the 

 year that the N.E. trade-winds of the Atlantic operate upon the 

 currents between 25"^ N. and the equator, log-books containing 

 no less than 380,284* observations on the force and direction of 

 the wind in that ocean were examined. The data thus afibrded 

 were carefully compared and discussed. The results show that 

 within those latitudes, and on the average, the wind from the 

 N.E. quadrant is in excess of the winds from the S.AV. only 

 111 days out of the 365. During the rest of the year the 

 S.W. counteract the effect of the N.E. winds upon the currents. 

 Now, can the N.E. trades, by blowing for less than one-third 

 of the time, cause the Gulf Stream to run all the time, and 

 without vaiying its velocity either to their force or their pre- 

 valence '? 



79. HerscheVs explanation. — Sir John Herschel maintains"]* that 

 they can ; that the trade-winds are the sole cause"^ of the Gulf 

 Stream ; not, indeed, by causing " a head of water " in the West 

 Indian seas, but by rolling particles of water before them some- 

 what as billiard balls are rolled over the table. He denies to 

 evaporation, temperature, salts, and sea-shells, any effective 

 influence whatever upon the circulation of the waters in the 

 ocean. According to him the winds are the supreme current- 

 producing power in the sea.§ 



80. Ohjedions to it. —This theory would require all the currents 

 of the sea to set with the winds, or when deflected, to be 

 deflected fi'om the shore, as billiard balls are from the cushions 

 of the table, making the littoral angles of incidence and reflection 

 equal. Now, so far from this being the case, not oxe of the 

 constant currents of the sea either makes such a rebound or sets 

 with the winds. The Gulf Stream sets, as it comes out of the 

 Gulf of Mexico, and for hundreds of miles after it enters the 



* Nautical Monographs, Washington Observatory, No. 1. 



t Article " Physical Geography," 8th edition Encyclopoedia Britannica. 



X "Tlie dj-uamics of the Gulf Stream have of late, in the Avork of Lieu- 

 tenant Maury, ah-eady mentioned, been made the subject of mucli (we caimot 

 but think misplaced) wonder, as if there could be any possible ground for 

 doubting tliat it owes its origin entirely to the trade-winds."— Art. 57, Phys. 

 Geography, 8th edition Encyc. Brit. 



§ Art. 65, Phys. Geography, Eucyc. Brit. 



