MECHANICS. 79 



Static*. 



In 1592, Galileo composed a treatise on statics, 

 which he reduced to this simple principle ; viz. It 

 requires an equal power to raise two different bodies 

 to heights having the inverse ratio of their weights; 

 that is, whatever power will raise a body of two 

 potonds to the height of one foot, will raise a body of 

 one pound to the height of two feet. 



The Vis Inertia of Nature. 



One of the grand laws of nature is, that all bodies 

 persevere in their present state, whether of motion or 

 rest, unless disturbed by some foreign power. Mo- 

 tion, therefore, once begun, would be continued for 

 ever, were it to meet with no interruption from ex- 

 ternal causes, such as the power of gravity, the resist- 

 ance of the medium, &c. 



The Lever. 



If the lever be 17 feet long, and the pivot or ful- 

 crum be a foot from one end, an ounce placed on the 

 other end will balance a pound placed on the near 

 end. If, instead of an ounce, we place upon the long 

 end the short end of a second beam or lever, sup- 

 ported by a fulcrum one foot from it, and then place 

 the long end of this second lever upon the short end 

 of a third lever, whose fulcrum is one foot from it ; 

 and if we put upon the end of this third lever's long 

 arm an ounce weight, that ounce will move upwards 

 a pound on the second lever's long arm, and this 

 moving upwards will cause the short end to force 

 downwards 16 pounds at the long end of the first 

 lever, which will make the short end of the first lever 

 move upwards, although 256 Ibs. be laid on it. The 

 same effect continuing, a pound on the long end of 

 the third lever, will move up a ton and three quar- 

 ters at the short end of the first lever, so that the 



