Meteorology, 509 
general atmosphere throughout, in the same 
vertual column, and subject to the common 
law of rarefaction in ascending. This isa 
view of the aqueous atmosphere, which no 
one seems to have entertained but myself. 
I have been making experiments almost an- 
nually on the subject since 1802, on the 
mountains in the North of England, and 
particularly on Helvellyn. These experi- 
ments have been materially facilitated of 
late years by masses of snow, which have 
been found near the summit, in the month of 
July; but it has often happened, that the 
cold springs of water near the summit, have 
been adequate. By one or other of these 
the dew-point of the air may be found at any 
required elevation on, the mountain, and. the 
law by which it is: regulated in the ascent, 
may be investigated.—On some future occa- 
sion, I intend to draw up a memoir on this 
subject. In the mean time I may observe, 
that all the phenomena concur in, exhibiting 
the same variation of density.in the aqueous 
vapour atmosphere in its present mixed state, 
as would no doubt be observed in an atmos- 
phere of pure steam of. equal density. 
