CHAPTER III 

 MECHANICS 



HAVING, in the preceding chapter, considered the first 

 elements of that branch of science which is the most 

 universal of all (since it relates to all things which can 

 be counted), we may now proceed to make some acquaint- 

 ance with the science which treats of the next most 

 general and obvious properties and powers of the sub- 

 stances and bodies which make up the world about us, 

 namely, with the science of Mechanics. 



We have hitherto only been concerned with ideas 

 of number, space, and direction, but in mechanics we 

 shall be compelled to deal with time, motion, and 

 force. 



All bodies known to us may be roughly arranged 

 in three groups: (i) a group of solids, such as pieces 

 of stone, metal, wood, &c. ; (2) a group of liquids', and 

 (3) a group of substances more or less like the air we 

 breathe, or like gas, and which are thence termed 

 aeriform or gaseous. Liquids and gases are also classed 

 together as fluids, on account of the ready mobility of 

 both. 



Any of these three kinds of bodies may be apparently 

 in a state of rest, or obviously in motion, and the study 

 of the various circumstances which attend these two 

 conditions of such bodies, constitutes the " Science of 

 Mechanics." 



