158 



BENJ. PIKE S. JR., DESCRIPTIVE CATALOGUE. 



is the force of the screw. Supposing the distance between 

 the spirals to be one quarter of an inch, and the length of 

 the winch to be six inches, the circle described by the 

 handle of the winch, where the power acts, is nearly 38 

 inches, or 152 quarter inches, and consequently 152 times 

 as great as the distance between the spirals ; and, therefore, 

 a power at the handle, where the power acts, of no more 

 than one pound, will balance 152 pounds acting against the 

 screw, and as much additional power as is sufficient to over- 

 come the friction, will raise the 152 pounds. 



Apparatus for the Composition and Resolution of Forces. 

 (Fig. 163.) This consists of a round table, usually about 

 18 inches in diameter, to the edge of which may be fixed 

 any number of brass pulleys, varying their direction at 



Fig. 1G3. 



pleasure. To use, place a circular paper upon the round 

 table, so that its centre may coincide with that of the table. 

 Upon this paper a triangle A B c is delineated, whose sides 



