338 Arialt/iis of Scientific Books. 



like the trunk and branches in the preceding comparison, pro- 

 gressively advances to the more recondite. For this reason, we 

 think that one of the earliest subjects to which the teacher ought 

 to direct a pupil's mind, is water ; first, in its various forms as 

 modified by temperature ; and next, as to purity and composi- 

 tion. The "disengagement of its two elements from their liquid 

 repose, having familiarized the mind to gaseous existences, he 

 will then readily enter on the chemical examination of the 

 atmosphere, and of the curious bodies resulting from the union 

 of its two constituents in successive multiple proportions. An 

 acquaintance with gasometry, and with Gay-Lussac's beautiful 

 doctrine of volumes, both essential to the ulterior investigations, 

 will thus be insensibly formed. 



The next transition in this natural order of tuition, may be 

 to the well known combustibles, sulphur and charcoal, and to 

 their several compounds with the bodies previously examined. 

 Common salt ought now to be carefully studied, particularly in 

 reference to its constituent chlorine. I he ores of a few leading 

 metals, with the principles of their reduction, and the metallic 

 oxides, chlorides, and alloys, may now come under review ; 

 after which the alkalis, earths, and their saline combinations, 

 with the acids previously examined, viz., the sulphuric, nitric, 

 and carbonic, will be natural objects of research. 



By such a course of experimental discipline, the diligent 

 student will acquire, almost imperceptibly, or at least without 

 any perplexity of intellect, a precise conception of the principal 

 objects and methods of chemical research. He may now pro- 

 ceed to examine the various acids and their bases, and the 

 combinations of one or other of these, with the metallic oxides 

 and metals. The salts, and the native mineral and organic 

 productions, will conclude !iis course. In proportion as he pro- 

 ceeds, the general facts of combination and decomposition, or 

 the laws of chemical affinity, will be developed and fixed in 

 his mind. 



Such may be reckoned the best mode of procedure in a 

 course of private study ; but transferred to a book, it would 

 evidently produce apparent disorder, though in reality far 

 more conducive to the instruction of the regular reader, 

 than those works which place the elementary bodies at the he- 

 grinning, and the more familiar bodies, or native compounds, 

 towards the end. This dilemma, between what best promotes 

 the symmetry of a printed treatise, and the edification of its 

 reader, is, with regard to arrangement, nearly unavoidable in 

 the present state of chemistry. The perception of this difficulty 

 has led chemists, at different times, to resort, with much ad- 

 vantage, to the dictionary form, or alphabetical order, for 

 dcBcribing the objects and phenomena of their science. Mac- 

 quer's Dictiooary was long a popular work all over Europe, 



