6 Dr. Darwin’s Account of 
two or three caufes, but particularly to the lefs con den fed Hate 
■of the air upon hills, which thence becomes a better conductor 
•of heat, as well as of electricity, and permits it to efcape the 
fafter ; it is from the water condenfeb on thefe cold furfaces of 
mountains, that our common cold fprings have their origin ; 
and which. Aiding between two of the -ft rat a above deferibed, 
defeend till they find or make themfelves an outlet, and will in 
confequence rife to a level with the part of the mountain where' 
they originated. And hence, if by piercing the earth you gain 
a fpring between the lecond and third, or third and fourth 
ftratum, it muff generally happen, that the water from the 
lowed; flratum will rife the higheft, if confined in pipes, be- 
caufe it comes originally from a higher part of the country in 
its vicinity. 
The increafmg quantity of this new fpring, and its increafing 
purity, I fuppofe to be owing to its continually diflolving a 
part of the earth it pafles through, and hence making itfelf a 
wider channel, and that through materials of lefs folubility. 
Hence it is probable, that the older and ftronger fprings are 
generally the purer ; and that all fprings were originally loaded 
with the foluble impurities of the ftrata, through which they 
trail fuded. 
Since the above- related experiment was made, I have read 
With pleafure the ingenious account of the King’s wells at 
Sheernefs, in the laft volume of the Tranfadlions, by Sir 
Thomas Hyde Page, in which the water rofe three hundred 
feet above its fource in the well ; and have alfo been informed, 
that in the town of Richmond, in Surrey, and at Infhip near 
Prefton in Lancashire, it is ufual to bore for water through 
a lower ftratum of earth to a certain depth ; and that when it 
is 
