WITH ELEVATION. 
309 
coalescing, generate minute drops, which, falling by their weight 
through the cloud, encounter and absorb fresh particles, thus 
continually increasing in size. But although this explanation of 
increase in the size of drops by aggregation of minute watery 
particles holds good in the clouds, I do not now think that it 
applies, under ordinary circumstances, to the increase (or 
apparent increase) in the quantity of rain which takes place in 
the strata of the atmosphere near the earth. Another explana- 
tion seems to me at once more simple and more complete. 
But this takes me to the second group of theories, namely, 
those which are based upon the assumption that the observed 
increase in the quantity of rain at the lower levels is mainly, if 
not entirely, illusory. 
And first among these theories comes one which may be easily 
shown to be fallacious, notwithstanding that it has been stoutly 
contended for by some able meteorologists. In the year 1871, in 
the columns of the Meteorological Magazine, it was my lot to 
take part in a controversy with the Kev. F. W. Stow, who had 
then lately broached the theory to which I am about to refer. 
Both Mr. Stow and myself were then under the impression that 
the theory was new ; but in science, as in other matters, history 
sometimes repeats itself, and I have since found that the same 
view had been put forward many years before by a Frenchman 
named Flaugergues,^ and that its fallacy had been more than 
once exposed. 
The theory, stated in Mr. Stow’s own words, is that the 
difference of the angle at which the rain falls is the real cause 
of the decrease of rainfall upon a horizontal surface with eleva- 
tion.”^ M. Flaugergues is still more explicit. He attempts to 
prove, mathematically, and with the aid of a diagram, that “ the 
I Annals of Philosophy ^ Vol. XIV., p. 114. 
2 British Bainfalli 1870^ p. 18. 
