188 OBSERVATIONS ON THE FALL OF RAIN. 
Most of the rivers, in this country, take their rise 
in mountainous or hilly districts. From the much 
greater quantity of rain which falls there, and the 
rapidity with which it flows from the steep decli- 
vities of the hills, it is evident that the principal 
supply to the rivers is there to be looked for. 
Dr. Dalton’s estimate, therefore, is probably 
much below the truth. 
If, then, both the depth of rain falling as a 
supply to rivers, and the quantity of water borne 
to the sea be taken at a higher rate than he has 
assumed, his calculations upon the evaporation 
from soil, &c. which must make up the difference, 
might still be probably correct, but on these, the 
Doctor himself places no dependance. 
It is clear that the best mode of ascertaining 
the real quantity of water evaporated from land, 
required for purposes of vegetation or absorbed 
by the ground, consists in observations similar in 
magnitude to those which have been attempted to 
be described. Garden experiments, upon a 
square box of a few inches, although they may 
be sufficient to illustrate the operations of nature 
to a philosophic mind, are not to be depended 
