'■2 CHEMISTRY. 



wliicli tlie comforts, and even the very existence, 

 of civilized life, depend. 



As exani])les, we may mention the arts of 

 dyeing, bleaching, tanning, potting, glass-making, 

 baking, brewing, distilling, working metals, &c. &c. 

 which owe their present state of perfection to the 

 science of chemistry In agriculture it is capable of 

 affording great assistance, by explaining the nature 

 of soils and manures; and in medicine its import- 

 ance is invaluable, many of the most efficacious re- 

 medies being entirely formed by chemical processes. 

 In short, there is scarcely any art or trade which 

 either does not altogether depend upon, or may be 

 benefited by this science. 



I3y chemical means we are enabled to reduce 

 compound bodies to the constituent principles of 

 which they are composed, and this operation is 

 called analysis, or decomposition. When a substance 

 cannot by any means be resolved into others, it is 

 called a simple body j and it is now known that 

 all that vast variety of substances which we see is 

 composed of a few simple bodies, which hence are 

 called elementary substances. 



Formerly, air, earth, Jire, and icater, were sup- 

 posed to be the elements of which all bodies were 

 formed ; but modern chemistry has shown that this 

 was an erroneous supposition. For the air, or at- 

 mosphere, is compounded of several distinct kinds 

 of aerial fluids or gases. Instead of one kind of 

 earth, it is now known that there are several kinds. 

 Water is no longer considered as an element, being, 

 in fact, formed of two substances very different, viz. 

 of oxygen and hydrogen. Fire is less understood, 

 and is still retained as an element under the name 

 of caloric. 



From the improvements that are continually 



