STUDY IV. 



195 



demonftrate, that their focus is not under the Line. 

 The caufe of their motions depends not on the at- 

 traflion, or the prelTure, of the Sun and of the 

 Moon, on that part of the Ocean ; for thefe forces 

 would, undoubtedly, aft there with the greateft 

 energy, and in periods as regular as the courfe of 

 thefe two luminaries ; but it feems to depend en- 

 tirely on the combined heat of thefe fame lumina- 

 ries, on the Poles of the Globe, the irregular effu- 

 fions of which, not being narrowed in the fouthern 

 Hemifphere, as in ours, by the channel of two ad- 

 jacent Continents, produce, on the (liores of the 

 Indian Ocean and South Sea, expanfions vague 

 and intermitting. 



It is fufficient, therefore, to admit thefe alter- 

 nate effufions of the polar ices, which it is impof- 

 fible to call in queftion, to explain, with the 

 greateft facility, all the phenomena of the Tides, 

 and of the Currents of the Ocean. Thefe pheno- 

 mena prefent, in the journals of Navigators the 

 moft enlightened, a perpetual obfcurity, and a 

 multitude of contradidions, as often as thefe fame 

 Navigators perfift in afcribing the caufes of them 

 to the conftant prciTure of the Moon and of the 

 Sun on the Equator, without paying attention to 

 the alternate Currents from the Poles, which direft 

 their courfe to that fame Equator ; to their coun- 

 ter-currents, which returning toward the Poles, 



o 2- produce 



