MECHANICAL PIIILOSOPII V. 235 



each other, so that, if one is increased, the other is diminished 

 in the same proportion. Great velocity in a machine, or in any 

 of its. parts, is incompatible with great power also; for whatever 

 js gained in speed is lost in strength, that is, it is gained at 

 the expense of power or force. 



It is not expected to gain power, force and velocity at the 

 same time by tho use of any mechanical contrivance whatever, 

 but, by taking a philosophical advantage of the few simple 

 mechanical powers, to obtain one or the other of them, accor- 

 ding to the labor to be performed. 



The advantages of machinery are numerous. 



1. By the aid of machinery we can apply force to much 

 better purpose than by our unassisted hands. 



2. A man can perform a work by its aid, to which he would 

 be wholly incompetent without it 



3. It often enables men to exert their whole force, where 

 without it they could exert only a small part of it. 



4. It enables us to employ animals in the execution of many 

 kinds of work which must otherwise be performed by man 

 himself. 



5. It enables us to employ several inanimate motive powers, 

 such as water, steam, wind," heat, electricity, &c. 



6. Many manufacturing operations are performed with much 

 greater facility and exactness than they could be by hand. 



7. Machinery saves a considerable part of the materials used 

 in the manufacture of many fabrics. 



ON REGULATING THE MOTION OF MACHINERY. 



The motion of machinery, to operate to the best advantage, 

 should be perfectly regular and uniform. Variations of motion 

 consist principally in variations of power, weight or resistances, 

 and changes of velocity in different parts of the machine itself. 

 The different instruments used to obviate these effects, and 

 secure uniform motion, are called regulators. There can be 

 little doubt that water, where it is abundant and available, 



