vapour upon its surface, unless its temperature, when at a 
height above the ground not exceeding that of the top of the 
tower of York Minster, is below — 434° Fahrenheit ! From 
this result it is evident that only a very small portion of the 
total augmentation of a rain-drop can be due to the condensa- 
tion of vapour upon its surface, and that by far the greater 
portion must be owing to the deposition of moisture which 
has already lost its latent heat, or heat of elasticity, and which 
is, therefore, not in the state of a true vapour, although, on 
the other hand, its invisibility in the atmosphere under 
ordinary circumstances, in the form of cloud or fog, renders it 
difficult to suppose that it can be in the ordinary liquid state. 
We have just seen that at a height of 356 feet, the quantity 
of rain is only one-half of that which falls on the ground; and 
it is evident, therefore, that a shallow stratum of the lower 
and comparatively clear atmosphere, supplies as much rain as 
a densely clouded, and much deeper stratum in the higher 
regions. As these remarkable results may raise doubts as to 
the general correctness of the methods of observation, which 
have been used to determine the quantities of rain at different 
heights, I may here mention an important fact, for which I 
am indebted to my friend, Mr. Binney, F.R.S. In descend- 
ing the shafts of deep coal mines, Mr. Binney has observed 
that the drops of water which drip from the upper part of the 
shaft increase to an extraordinary size during their descent to 
the bottom. Evidently the same principle is here in opera- 
tion as in the case of a rain-drop falling through the atmo- 
sphere, and Mr. Binney ’s observation affords a valuable 
confirmation of the general accuracy of the results of the 
observations which have been made to determine the rain- fall 
at different elevations. 
That the whole amount of a fall of rain is not derived from 
the direct condensation of vapour at the time that the fall 
takes place, is apparent from other considerations than those 
which depend upon the different (piantitics of rain at different 
