MEASURE OF MOVING FORCE. 147 
son, Poncelet, and Moseley, and seems likely to 
be generally followed. 
A unity of work, in the sense here used, is, in 
this country, represented by the labour of remoy- 
ing one pound through one foot; and, in France, 
one kilogramme through one metre. With these 
values any other quantities of work may be com- 
pared. As, for instance, if 2240lbs., or one 
ton, be raised through ten feet, the work done 
will be 2240 x 10=22400 lbs., or ten tons raised 
through one foot, representing 22400 unities of 
work. 
If p be any constant pressure tending to do 
work, and s the space through which it has acted, 
then ps will be the work done; and this quan- 
tity of work will be the same if p be increased 
or decreased in any proportion, provided that s 
be decreased or increased in the same proportion, 
since the quantity of work depends upon the 
product of the two, and not on the value of 
either. 
WORK DONE BY GRAVITY. 
To compare the quantity of work ps with the 
effects of gravity in the falling of bodies, suppose 
