68 OUTLINES OF NATURAL PHILOSOPHY. 



SECT. II. 



OF THE MECHANICAL POWERS. 



5. J\. MECHANICAL power, is an instrument 

 by which the effect of a given force is increased, 

 while the force itself remains the same. 



The simple mechanical powers into which more com- 

 plex machines are resolved, are these : 1. The Le- 

 ver ; 2. The Wheel and Axle; 3. The Pulley; 

 4. The Wedge ; 5. The Screw : 6. The Funicular. 

 Machine. 



Of the Lever. 



123. DEF. A lever is an inflexible rod, move- 

 able about a centre or fulcrum, and having forces 

 applied to two or more points in it. 



a. The simplest state of the lever is, when there are 

 only two forces ; and of this there are two cases : 

 in the first, the fulcrum is between the points where 

 the forces are applied, and the forces are directed 

 the same way; in the second, the points to uhich 

 the forces are applied, are on the same side 'of the 

 fulcrum, and the forces are directed opposite ways. 



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