Aqueous Vapour Atmosphere. 123 
Thisends the series of observations on the 
mountains; which I may perhaps be allowed 
to say are original in their nature and design. 
Though they do not demonstrate the existence 
of an atmosphere of vapour that is perfectly 
conformable to the known laws of the com- 
mon atmosphere at large, they seem to es- 
tablish several important points. 
1st. That the quantity and density of va- 
pour is constantly (or with very rare excep- 
tions) less the higher we ascend. 
2d. That wherever a dense cloud or fog 
exists, there the temperature of the air and. 
the dew-point are the same. 
3d. That when a mountain is wholly or in 
great part enveloped in fog, there is little 
variation in ascending either in the temper- 
ature of the air or in the dew-point. 
4th. That upon an average the temperature 
of the air sinks after the rate of 1° for every 
80 yards perpendicular ascent, about the 
middle or warmest part of the day ; and that 
of the dew-point 1° for every 130 yards per- 
pendicular ascent. 
5th. That the phenomena of aqueous me- 
teors, such as rain, fog, dew, &c. depend 
upon the known relations of heat and water, 
and are exhibited to us in miniature every 
day in our domestic economy. Electricity 
