46 Questions Jbr Solution relating to Meteorology, 



of Mexico ; and, lastly, that kind of cascade formed by the ac- 

 cumulated water in the Gulf, where it escapes from the Strait of 

 Bahama, the continuation of which forms the gulf-stream. 



With respect to the current flowing towards the Straits of 

 Gibraltar, it may be caiised by the lower level of the Mediter- 

 ranean, and this depression of its surface may itself be occasion- 

 ed by its excessive evaporation which the influx of the tributary 

 rivers is insufficient to compensate. 



These explanations are simple ; they appear to rest on phy- 

 sical causes, the action of which must take place in the sense 

 supposed ; the most intelligent observers, Franklin, Rennel, &c., 

 have adopted them ; and yet I am about to prove that they are 

 not so completely established by observation, measurement, and 

 experiment, as to prevent us from entertaining legitimate doubts 

 on the subject. 



A continued and strong wind raises the level of the sea along 

 the coast towards which it tends to direct the water ; thus, at 

 Brest, Lorient, Rochefort, &c., the tide is always highest, other 

 circumstances being equal, during a west wind. On the oppo- 

 site shores of the Atlantic, and along the coasts of the United 

 States, on the contrary, it is the east wind which produces this 

 effect. It is by south winds that the waters of the Mediterra- 

 nean are accumulated in the ports of Genoa, Toulon, and Mar- 

 seilles, and by north winds in those of Algiers, Bougie, and 

 Tunis. These facts are not disputed, nor do they admit of be- 

 ing called in question. It only remains to determine the value 

 of the accidental changes of level which winds may produce. 



Franklin relates that, in an extensive piece of water three 

 leagues broad, and about three English feet in depth, a strong 

 wind caused the whole of one of the sides to become dry, while 

 it raised the water on the opposite side three feet above its for- 

 mer level, the depth being six feet instead of three, Irr our own 

 seas, I do not think that it will be necessary, in general, to state 

 a higher number than this as the maximum effect produced by 

 the most violent tempests.* 



The Trades are constant winds, but their strength is very mo- 



• Places are mentioned in the Mediterranean where gusts of the south- 

 west winds (named the Labeschades) have raised the waters seven metres 

 above their ordinary level ; but this effect was purely local. 



