and to dissipate Storms. 215 
Next follows in the above memoir the indication of the 
only preservative against hail, suggested by naturalists, being 
the establishment of a multiplicity of thunder -rods. 
Before entering into the detail of the new methods he 
submits to the judgment of the learned, M, Denize pro- 
ceeds to lay before them the results of his own observations 
upon the formation of hail. It will not be out of place to 
follow him in this branch of his subject. 
I think we may thus state the principles upon which the 
author’s opinion is founded : 
The elements which enter into the composition of storms 
are, the atmospheric air, water, electricity, and caloric. 
Water dilated by caloric is formed into vapours, and be- 
comes specifically lighter than the atmospheric air; it 
ascends, and carries with it a quantity of electricity propor- 
tioned to the capacity it has just acquired. 
If the air in which these vapours are suspended is of a 
temperature lower than theirs, they condense, by the disen- 
gagement of their caloric, into clouds more or less thick. 
Under this new form, their dimensions being diminished, 
they contain a superabundant quantity of electricity, which 
they may get rid of by communication either with others or 
with the earth by means of conductors ; but aftera time they 
will be less electrified, if, by traversing some streams of air 
abounding in caloric, they resume their former state of dila- 
tation, 
It is from the contact of clouds variously electrified that 
storms are produced, the electric fluid darting successively 
from one cloud to another in order to obtain an equilibrium. 
As the author explains the formation of drops of. rain 
during storms, and afterwards drops of hail, in a manner 
peculiar to himself, that is to say, by referring their forma- 
tion to the concussion occasioned in the atmosphere of the 
clouds by claps of thunder, I shall quate his own words on 
the subject : 
** As soon as the thunder begins to explode in the apart 
of the storm, the explosion shakes every part of the sur- 
rounding air, at the same time that it suddenly diminishes 
O 4 its 
