Dr. Turner's Elements of Chemistry. 6t 



Light is next treated of, but we think too hastily, and too 

 much in the abstract. 



Now the subjects of heat and light are obviously of the 

 utmost importance to the chemical philosopher, and they are 

 very extensive, and intricate and difficult to treat of, inasmuch 

 as the writer is necessarily upon the confines of chemical and 

 mechanical philosophy, and should be expert in both. When, 

 therefore, elementary works on chemistry are so written and 

 arranged as to serve as text-books for lectures, and indexes 

 of reference to more accurate information, we can make due 

 allowance for brevity ; but when the subject is intended to 

 be formally and completely developed to the student, inde- 

 pendent of other ocular and oral aids, much more extensive 

 description and detailed explanation is required, than is to 

 be found either in our author's '* Elements," or in any other 

 analogous condensation of chemistry. Dr. Henry under- 

 stands the requisite mode of conveying information in these 

 cases better than most writers ; and when he takes pains, 

 and speaks for himself, has the talent of being brief, and at 

 the same time minute, deep, and clear. Dr. Ure, as his 

 dictionary shows, is an eminent example of such a writer — > 

 he of course is neglected, where, as with our author, Dr. 

 Thomson is in the ascendant; but the article caloric, in his 

 dictionary, will at once explain and illustrate our meaning, 

 and would furnish an admirable foundation for a detailed 

 essay or treatise upon the subject. So extensive, indeed, 

 are the precincts of chemistry now becoming, that either 

 our systems must become very voluminous, or we must 

 adopt the plan, which to us appears preferable, of distinct 

 treatises upon different branches of the science. Thus, a 

 separate work on heat and light ; another on electricity and 

 magnetism ; another on attraction and the theory of combi- 

 nation ; a fourth on the constitution and properties of the 

 unmetallic elementary bodies ; a fifth on the metals and their 

 compounds; a sixth on vegetable, and a seventh on animal 

 chemistry and physiology ; an eighth on the chemistry of the 

 arts ; and lastly, a treatise on chemical manipulation in ge- 

 neral, would include all that appears essentially requisite ; 

 and as no one is supposed to be equally well versed in all 

 branches of the science, or in all details of the art, an 

 opportunity of selection would thus be afforded, so that each 

 writer might choose that particular department which he is 

 most accurately acquainted with, or which has formed his 

 favourite study. Mr. Faraday has already, as may be said, 

 led the way in such a plan, by the publication of his Chemi- 



