138 HISTORY OF 



yet we very well know, that scarcely '^lineteen inches of rain-water 

 falls in that time: ^o that evaporation would carry off a mueii 

 greater quantity than is ever known to descend. The small 

 quantity of rain-water that falls is, therefore, but barely suffi- 

 cient for the purposes of vegetation. Two leaves of a fig-tree 

 have been found, by experiment, to imbibe from the earth, in tire 

 hours and a half, two ounces of water. This implies the great 

 quantity of fluid that must be exhausted in the maintenance of 

 one single plant. Add to this, that the waters of the river Run- 

 gis will, by calculation, rise to fifty inches ; and the whole coun- 

 try from whence they are supplied newr receives fifty inches in 

 the year by rain. Besides this, there are many salt springs, 

 which are known to proceed immediately from the sea, and are 

 subject to its flux and reflux. In short, wherever we dig beneath 

 the surface of the earth, except in a very few instances, water is 

 to be found ; and it is by this subterraneous water that springs 

 and rivers, nay, a great part of vegetation itself, is supported. It 

 is this subterraneous water which is raised into steam, by the 

 internal heat of the earth; that feeds plants. It is this subter- 

 raneous water that distils through interstices ; and there, cooling, 

 forms fountains. It is this that, by the addition of rains, is in- 

 creased into rivers, and pours plenty over the whole earth.'* 



On the other side of the question', it is asserted, that the 

 vapours which are exhaled from the sea, and driven by the winds 

 upoti land, are more than sufiicient to supply not only plants 

 with moisture, but also to furnish a sufficiency of water to the 

 greatest rivers. P'or this purpose, an estimate has been made 

 of the quantity of water emptied at the mouths of the greatest 

 rivers ; and of the quantity also raised from the sea by evapora- 

 tion ; and it has been found, that the latter by far exceeds th 

 former. This calculation was made by Mr Marriotte. By him 

 it was found, upon receiving such rain as fell in a year, in a pro- 

 per vessel fitted for that purpose ; that one year with another, 

 there might fall about twenty inches of water upon the surface 

 of the earth, throughout Europe. It was also computed that 

 the river Seine, from its source to the city of Paris, might cover 

 an extent of ground, that would supply it annually with above 

 eeven millions of cubic feet of this water, formed by evaporation. 



1 Phil. Trans, vol. ii. p. ViS. 



