THEORY OF CLOUDS. 
365 
be vesicular or not, if it be water, must be heavier 
than air, and will consequently descend. After 
a certain distance accomplished in its descent, the 
aqueous vapour perhaps passes into a stratum or 
patch of comparatively dry air, or air not satu¬ 
rated with moisture, where the attraction of the 
air for water will necessarily occasion the solution 
of the vapour, and its disappearance. Thus we 
can account for the suspension of clouds on prin¬ 
ciples universally known and admitted. The 
steady form and position sometimes maintained 
by the clouds in the open atmosphere, I appre¬ 
hend to be, as in those on the tops of mountains, 
rather apparent than real;—the visible suspen¬ 
sion being the effect of continual condensations 
of moisture on the upper, and solutions on the 
lower parts. 
For a further illustration of this opinion, let us 
suppose three horizontal strata of air, a, b, c, in a 
vertical series, at a considerable altitude, and in 
different states or velocities. Let the two upper 
