460 Analyses of Books, [Dec. 



It is a bad omen to stumble at the threshold, but we cannot 

 help it ; Mr. Gray thus defines chemistry : — " The alterations 

 and appearances that take place in the admixture of bodies, and 

 the action of heat and cold upon them, are the proper objects of 

 chemistry; which also endeavours to explain the production of 

 similar phenomena when they arise from other causes." 



Now unless cold be a positive power, which we suppose Mr. 

 Gray will not contend that it is, the effects of cold are referrible 

 to alterations of temperature, and consequently to the subject of 

 heat itself; what the similar phenomena are which arise from 

 other causes besides chemical action, we are quite at a loss to 

 QOnjecture. 



After giving the theory of combustion, which we must pass 

 over without remark, Mr. Gray proceeds (p. 189) to the consi- 

 deration of the 



" Compound Combustibles. — The more simple substances being 

 thus gone through, it remains only to treat of those compound 

 combustibles, which are, generally speaking, produced in organic 

 bodies, or from bodies having that origin. Some of them, 

 indeed, are so loaded with water or other incombustible matter, as 

 vinegar or oyster shells, that they appear, to a common observer, 

 to be themselves incombustible ; but when the water or other 

 extraneous matter is separated, this appearance vanishes. In 

 point of chemical composition, they are, generally speaking, 

 compounds of carbon, hydrogen, and oxygen, to which are 

 sometimes added nitrogen and other ingredients : hence they 

 are distinguished from the combustibles of the former series, in 

 always forming both carbonic acid and water by their union 

 with more oxygen." 



Some further observations succeed the above, and we then arrive 

 at the " Pharmaceutical Division of Combustibles; " and Mr. G. 

 informs us, that the divisions which the " pure chemists " have 

 formed, are not followed in his work. ''Spirit of wine and vinegar, 

 being of continual use in chemistry, as agents in the preparation and 

 examination of bodies, are first noticed ; and the remainder of 

 the combustible bodies are arranged according to their taste, as 

 being the quality that is usually first attended to in examining 

 them, and which has also a considerable connexion with their 

 medical virtues. For the sake of elementary brevity, scarcely 

 any other of these articles but those enumerated in the Materia 

 Medica of the London College of Physicians are noticed. The 

 arrangement of these combustible drugs is as follows : 



1. Earthy and absorbent bodies. 



2. Farinaceous, mucilaginous, gelatinous, gummy, and 

 emollient bodies. 



3. Bitter bodies. 



4. Austere and acerb bodies. 



5. Acid bodies. 



6. Aromatic bodies. 



