OBSERVATIONS ON THE FALL OF RAIN. 159 
various rivers in the country; the result is, that 
he considers 13 ins. of the annual rain are in 
that way disposed of, and that 23 ins. remain to 
be accounted for. This brings him to a consi- 
deration of the quantity of water raised by evap- 
oration. ‘To ascertain this point, not finding the 
observations of others sufficient for his purpose, 
he made various experiments upon the evapora- 
tion from soil. From these it seemed that the 
evaporation amounted to 25 ins. of rain annually, 
and if 5 ins. for the dew were added, it would 
give 30 ins. of water raised annually. As this 
exceeded the medium reserve of 23 ins., he goes 
on to enquire ‘whether the rain is adequate, or 
whether the earth derives a supply of water from 
some subterraneous reservoir, according to the 
opinion of some philosophers.’”’ Having accounted 
for this apparent discrepancy, he finally arrives 
at the conclusion “that the rain and dew of this 
country are equivalent to the quantity of water 
carried off by evaporation, and by the rivers.” 
He finally examines the various opinions which 
at that time existed upon the origin of springs, 
concluding that they must be attributed solely 
to the rain, their variation depending upon the 
seasons, and upon the quantity of rain which falls. 
