308 
ON THE DECEEASE OF KAIN 
view is certainly untenable. The drops may increase in size by 
the aggregation of minute liquid particles. We must bear in 
mind the distinction between the gaseous and the liquid forms 
of water. Water* vapour is a dry gas, and the quantity of it 
that can be condensed into liquid under given circumstances is 
strictly limited, admitting of exact calculation. But there is no 
such limitation to the amount of liquid water that may be 
absorbed by falling drops, supposing such to be encountered by 
the drops in their descent. It was this view that led me ten or 
eleven years ago to put forward a theory which I was then sanguine 
enough to believe fully met the case.^ I conceived that the 
lower strata of air during rain might be charged with minute 
watery particles which were caught up and incorporated by the 
falling drops of rain. I gave reasons for believing in the 
probable presence of these watery particles, I showed why they 
should not under ordinary circumstances take the form of visible 
cloud ; why they should be most abundant in the very lowest 
strata, where we have seen the greatest effect to be produced ; 
and why the operation of this cause should be most effective in 
windy weather — the condition under which (as I shall presently 
explain more fully) all observers have found the difference to be 
greatest. 
Whatever view may be taken of the value of this theory as 
an explanation of the phenomenon now under discussion, there 
can be little doubt that it represents what takes place in the 
original formation of rain. The constituent particles of a cloud, 
it should be remembered, are not vapour, but liquid water in a 
finely divided state. When rain is being formed, these particles, 
^ The author has lately found, in the British Association 
Bejport for 1834, p. 563, an abstract of a paper by Mr. Luke Howard, 
in which a theory is propounded similar in its leading feature to his 
own (now discarded) theory. 
