1822.] Composition of Common Verdigris. 165 
M. Chaptal in his “ Chimie appliquée aux Arts,” mentions the 
silky blue crystals as forming on the surface of the plates of 
copper in the preparation of French verdigris. As far, however, 
as my knowledge extends, no analysis of them has yet been 
given; this is the more remarkable, because the existence of 
these crystals may be considered as indicative of the perfection 
of the manufacture. 
ARTICLE II. 
Experiments and Calculations for comparing the Force of a Body 
in Motion with Dead Weight. By Col. Beaufoy, FRS. 
(To the Editor of the Annals of Philosophy.) 
DEAR SIR, Bushey Heath, Stanmore, Aug. 10, 1822. 
In the last century, a remarkable difference of opinion sub- 
sisted among philosophers respecting the momentum of bodies. 
The English and French mathematicians maintained that the 
momentum was the weight multiplied into the simple velocity. 
The Dutch, German, and Italian philosophers, on the contrary, - 
asserted that the momentum was the mass multiplied into the 
square of the velocity. This controversy appears to have been 
conducted with a great deal of asperity, and in some instances 
recourse was had to personal abuse. 
The experiments to which the disputants appealed in support 
of their arguments not being satisfactory, has induced me to turn 
my attention to the subject, and endeavour to contrive an appa- 
ratus for making a series of experiments less liable to objection. 
How far this undertaking has been attended with success, is 
submitted to the readers of the Annals of Philosophy ; but I 
think I have proved that a moving solid and a dead weight are 
not incommensurable with each other. 
It is evident that when a stake is driven into the ground by a 
beetle, or a pile into the earth with an engine, the wood sinks 
lower and lower until the resistance it meets with equals the 
impetus of the impelling power; and then it becomes an accu- 
rate measure of the momentum of the descending ram. The 
only difficulty in this investigation consists in finding the resist- 
ance the pile meets with. To accomplish this purpose, I caused 
to be made a well-formed spiral spring, and inclosed it in a 
cylinder of brass. This represents the opposition of the ground 
to the entrance of the pile. 
Through the centre of the cylinder and the middle of the 
inclosed helical spring, was inserted a circular brass rod ; this 
may be considered as representing the pile to be driven, and 
was sufficiently long to project beyond each extremity of the 
