320 OUTLINES OF NATURAL PHILOSOPHY. 



by 31026124800, or nearly an eighth part of the 

 whole, which is therefore left to be taken up by the 

 evaporation. 



MARIOTTE has made a similar computation for the 

 Seine, in his Traite de Mouvemeni des Eaux. 



432. The disputes that prevailed so long con- 

 cerning the origin of fountains and rivers, chiefly 

 arose from the difficulty of conceiving, how a pre- 

 carious and accidental supply could be rendered 

 equal to a regular and great expenditure. 



The opinions of the ancients, concerning the origin 

 of fountains, are to be found in SENECA, Nat. Quocst. 

 lib. in. See also VARENIUS, sect. iv. chap. xvi. 

 prop. 5. 



433. The quantity of rain that falls in different 

 places in the same year, and in the same place in 

 different years, is extremely various ; and even in 

 the temperate zone runs between the extremes of 18 

 and 100 inches. 



In places not very distant from one another, the dif- 

 ference in the quantity of rain is often very great. 

 The neighbourhood of the sea on one hand, and 

 mountains on the other, is most favourable to the 

 production of rain ; from the first is derived a hu- 

 mid 



