On Rain, Evaporation, &c. 971 
in depth, ‘so ‘saturated, contains ‘7 inches’ of 
water, and that it may part with one quarter of 
its water, or even one half, and not be too dry 
for supporting vegetation. 
Clay, just dug out for the purpose of watts 
bricks, was tried in the same manner: It gave 
the same specific gravity as the earth, and yielded 
not much less water, 
These experiments and observations prove, 
that M. dela Hire’s conclusions, drawn fbi 
the vegetation of plants in a given quantity of 
soil, precluded from any communication with 
the earth at large, are erroneous, or at least un- 
warranted: As it does not thence appear that the 
evaporation for the whole year exceeds the rain 
in the year, whatever it ai ‘do for a month or 
two in summer. -* 
The origin of springs may still therefore be 
attributed to rain, till some more decisive ex- 
periments appear to the contrary; and it be- 
comes unnecessary to controvert the other two 
opinions respecting this subject. 
Upon the whole it should seem, that at the 
commencement of spring, the ground is nearly 
saturated with water for 5 or 6 feet in depth, as 
the rains and dews in autumn and winter far ex- 
ceed the evaporation: There are then 5 or 6 
inches of water at least tobe raised up again to ° 
the surface in case of exigence in the spring and 
