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The endeavour to follow out to precise mathematical results 
the phenomenon of rain, would be met by at least as many 
difficulties, as would a similar attempt, in the case of any 
other of the natural phenomena. 
The great number of agents at work in the production of 
rain, and the manner in which they act and re-act upon one 
other, each being at the same time influenced by local cir- 
cumstances in an infinite variety of ways, makes the pheno- 
mena of atmospheric condensation extremely complicated. 
For instance, suppose the process to have just commenced, 
by the influence of a cold mountain summit upon a warm and 
humid atmosphere, the first step is the transformation of the 
vapour into the watery vesicles of which clouds and fog are 
composed, simultaneously the latent heat of the condensed 
vapour becomes sensible, and is distributed around, tending 
to check the energy of the scarcely begun process. Then, the 
opaque clouds assumes a power which the transparent vapour 
had not ; — it becomes capable of losing heat by radiation, as 
well as of intercepting the radiant heat coming from the sun 
or earth, or neighbouring clouds. 
Again, the two component parts of the atmosphere, name- 
ly the aqueous and the dry, have different affinities for heat ; 
that is they are not equally affected by the same increment or 
decrement of temperatui*e, so that when a change of tempera- 
ture takes place a disturbance of their relations ensues, and 
each component part of the atmosphere acted upon, has to go 
and seek a new place of equilibrium in the vertical column. 
Besides all this, the act of condensation is accompanied by 
electrical action, which no doubt introduces new modifications 
into the result. 
Thus each step of the process causes the introduction of 
new agents to the work ; all acting upon one another and 
tending to modify the energy of action of each of the forces 
in play. 
Of course, there is nothing like chance, or accident in the 
ever changing action of these mingled forces ; they are all 
wonderfully adjusted so as to produce a result beneficial to 
man, namely, a well regulated supply of rain. Each of the 
agents mentioned, and perhaps many others of which we are 
