INTRODUCTION. 15 



mulated, in the practice of the arts, and in domestic economy, long 

 before any general truths were established, by a course of inductive 

 reasoning, upon the phenomena. 



The arts are all either mechanical or chemical, and not unfrequent- 

 ly both are involved in the same processes. The practices of the 

 arts may be regarded as experiments in natural philosophy and chem- 

 istry. The object of the artist is usually gain ; but he, or any other 

 person, who views the facts correctly, may reason upon them advan- 

 tageously, and thus obtain important instruction. 



Glass is a chemical compound, usually of siliceous earth and fixed 

 alkali, or in a more extended view, of alkaline, saline, metallic and 

 earthy materials. These, after being duly proportioned, are com- 

 bined by the effect of fire, and various adventitious matters are added, 

 to impart color or to discharge it, to increase the density, or to dimm- 

 ish the hardness, or for various other purposes. 



The production of the materials of the glass depends therefore 

 upon chemical principles, and is thus far, a chemical art. But, the 

 fabrication of the vessels depends upon mechanical causes, principally 

 the breath of the artist, injected through an iron tube, to which the 

 melted glass is made to adhere. The subsequent cutting, grinding, 

 and polishing of the glass are also mechanical, and thus glass is a 

 production both of chemistry and mechanism. 



Soap, (except the mere act of mingling the oil and the alkali,) is a 

 production of chemistry alone ; a watch is a result of mechanism, but 

 the metals of which it is made are prepared by chemistry and me- 

 chanism united ; wool is carded, spun, woven, fulled and sheared by 

 mechanical means, but it is scoured and dyed by chemical processes, 

 and thus through a multitude of instances, the purposes of society are 

 accomplished, by the application of the principles of one or of the 

 other, or of both of these sciences. 



The science of chemistry considered as a collection of elementary 

 truths derived from the study of facts, can scarcely be referred to a pe- 

 riod much beyond the commencement of the last century, and its prin- 

 cipal triumphs have been achieved, since the middle of that period. 

 It would be premature, to detail, on the present occasion, the partic- 

 ular discoveries, which, like stars, rising successively, above the hor- 

 izon, have broken forth in rapid succession. Those discoveries, their 

 periods and authors will be mentioned, in giving the history of each 

 particular substance. At present, it would not be proper to attempt 

 any thing more than to convey to those to whom the subject may be 

 new, a general conception of the nature, extent and objects of the 

 science of chemistry, reserving the details for the time when they 

 will be both the most intelligible and the most interesting. > 



