320 On Printing Presses and their Theory. a” 
SUPPLEMENT. 
As the power gained by different pambientions like those 
referred to in the preceding pages seems to have scarcely 
attracted the notice of writers on Mechanics, I shall subjoin 
an investigation of such as are most likely to occur in prac- 
tice, for the information of those who may be concerned in 
invention or improvement of machines which contain 
combinations, and to whom it may be sometimes im- 
portant to know with precision the ‘mechanical advantage 
they gain by different supposed arrangements of machinery, 
and the strain to which the different parts are subjected. 
Pror. 1. Let €B (Plate Ill. Fig. 1.) be a straight rod, 
moveable about C, and BA another rod, connected by a 
joint with CB at B, and wits its other extremity A confined 
to atccar in the line Oey duced : it is required to deter- 
wer will be to the resistance, in dae, as in all oth- 
er cases, in the inverse ratio of the velocities of their re- 
spective points of application. We have therefore only to 
investigate, for any given position of B and A, the velocity 
hi moves, or the circular arc DB increases, 
compared with eet of A’s motion on the line CA. For fC 
‘ purpose, draw the endicular BP, put AB= 
B=b, AC =¢, BP oy, jd DAs. Then “go vara 
= i eS ; By dy ayy. 
viey 23; and taking the fluxions, dr= Vang Tee Te 
- But beat hence hy division = reas ay s?—s5 dale +e 
: ate Cl 
_sin ABC _ sin 
= pac RAC hide: the pow- 
er is to the resistance overcome, as the sine of the angle. 
a 
