LECTURE XXV. 

 CHEMISTRY. 



GENERAL PRINCIPLES. 



CHEMISTRY has been termed, with some pro- 

 priety, the anatomy of matter : and its object is to 

 discover the component parts of bodies, and, if 

 necessary, to form them into new combinations. 

 This last, indeed, is the principal occupation of 

 the practical or trading chemist. 



It is by the agency of heat and mixture, or, in 

 other words, by the action of the particles of one 

 body upon those of another, that the chemist is 

 enabled to analyse or decompose the different 

 substances which nature presents to his view. 

 The matter of heat, or caloric, is the most power- 

 ful agent; for it has an attraction for most bodies, 

 enters into their pores, and by its repulsive powers 

 produces a decomposition of their constituent 

 particles. There exists also in many cases a re- 

 ciprocal attraction between the particles of one 

 substance and those of another: this is seen par- 

 ticularly in all cases of solution ; as when a lump 

 of loaf sugar is put into a glass of water, it is said 

 to be dissolved ; that is, the particles of the sugar 

 are intimately blended and united with those of 

 the water by a mutual attraction. Here let it be 

 observed that mere mechanical mixture is very 



