360 On Rain, Evaporation, &c. 
in such circumstances will be 17 or 18 inches, 
which is but half that observed from water at 
Liverpool, and 6 inches less than the reserve of 
rain stated above. 
In order to ascertain this point more fully, 
and to investigate the origin of springs, my 
friend Thomas Hoyle, jun. and self practised 
an -expedient as follows, beginning in the au- 
tumn of 1795. Having got a cylindrical vessel 
of tinned iron, 10 inches in diameter and 93 
feet deep, there were inserted into it two pipes 
turned downwards for the water to run off into 
bottles: The one pipe was near the bottom of 
the vessel; the other was an inch from the 
top. The vessel was filled up for a few inches 
with gravel and sand, and all the rest with good 
fresh soil. It was then put into a hole in the 
ground and the space around filled up with 
earth, except on one side, for the convenience of 
putting bottles to the two pipes; then some water 
was poured on to sadden the earth, and as much 
of it as would was suffered to run through with- 
out notice, by which the earth might be con- 
sidered as saturated with water. For some weeks 
the soil was kept above the level of the upper 
pipe, but latterly it was constantly a little below 
it, which precluded any water running off 
through it. Moreover, for the first year the 
soil at top was bare; but for the two last years 
