Bodies affeSied by Friction, i ~ j 
retardation vanes as - Qua „ ti;y of - 1M „ er ; hence, if a body be put 
in motion upon the horizontal plane by any moving force, if 
both the weight of the body and the moving force be increafed 
in the fame ratio, the acceleration arifng from that moving 
force will remain the fame, becaufe the accelerative force varies 
as the moving force divided by the whole quantity of matter, 
and both are increafed in the fame ratio ; and if the quantity 
of fri£Hon increafes alfo as the weighr, then the retardation 
arifing from the fri&ion will, from what has been faid, remain 
the fame, and therefore the whole acceleration of the body will 
not be altered ; confequently the body ought, upon this fuppo- 
fition, fill to defcribe the famefpace in the fame time. Hence, 
by obferving the fpaces defcribed in the fame time, when both 
the body and the moving force are increafed in the fame ratio, 
we may determine whether the friftion increafes in proportion 
to the weight. The following experiments were therefore 
made in order to afcertain this matter. 
Exp. i. A body weighing io oz. by a moving force of 4 oz. 
defcribed in z" a fpace of 51 inches; by loading the body with 
10 oz. and the moving force with 4 oz. it defcribed 56 inches 
in z " ; and by loading the body again with 1 o oz. and the 
moving force with 4 oz. it defcribed 63 inches in z " . 
Exp. 2. A body, whofe weight was 16 oz. by a moving 
force of 5 oz. defcribed a fpace of 49 inches in 3^ ; and by 
loading the body with 64 oz. and the moving force with 20 oz t 
the fpace defcribed in the fame time was 64 inches. 
Exp. 3. A body weighing 6 oz. by a moving force of z\ oz. 
defcribed 28 inches in z ,r ; and by loading the body with 24 
oz. and the moving force with 10 oz. the fpace defcribed in the 
fame time was 54 inches. 
Z 2 Exp. 
