440 Notices respecting New Books. 



as they deserve, have many admirers. The facts are here accurate, 

 and the manner in which they are introduced, as well as the peculiar 

 treatment of the whole subject, leave uo doubt upon the mind that 

 the author is perfectly ;it home, and speaks from his own experience. 

 It is only as critics tliat we feel it to be our duty to draw attention 

 to a slight absence of strictness and philosophic accuracy in some of 

 the theoretical questions introduced ; before doing so, however, let 

 us admit that these defects diminish but little the value of the les- 

 sons ; indeed, their general excellence suggests, in some measure, 

 that closer examination which has led to the detection of what we 

 deem to be faults. For instance, great an 1, we think, undue stress 

 is laid upon the elective character of the chemical force, by which it 

 is thought to be distinguished from all other natural forces. "If," 

 says the author, " we place a piece of silver and a piece of iron in a 

 tumbler of water, we notice after the lapse of a few days that the 

 iron has lost its lustre and become covered with rust, whilst the 

 brilliant surface of the silver remains unchanged. Here one of the 

 constituents of the atmosphere, oxygen, which was dissolved in the 

 water, finding itself in the presence of silver and iron, made a selec- 

 tion between the two metals, and preferring the iron, united exclu- 

 sively v.ith that metal." This is quite true, but it can scarcely be 

 considered characteristic of the chemical force ; for Professor Frankland 

 knows quite well, that if a magnet were presented to the same two 

 pieces of metal, it would manifest precisely the same preference, and 

 make exactly the same selection. Again, the term elasticity is used in 

 a rather obscure manner. Let us suppose that the young reader has 

 turned to the very useful appendix at the end of the book, and found 

 elasticity defined, very properly, as " the property which some bodies 

 have of recovering their form and dimension after the force which 

 changed their shape and appearance is withdrawn," and then imagine 

 his confusion when he reads the following sentences : — " Heat is the 

 principle oi elasticity." — "Just as cohesion modifies chemical affi- 

 nitj, &.C., so heat or elasticity produces analogous results by the 

 formation of volatile compounds, and their expulsion in the gaseous 

 form." Or lastly, "the mode of decomposition being here deter- 

 mined by the elasticity of the carbonate of ammonia, which is ex- 

 pelled from the mixture in the form of white vapours." It ma}'^ be 

 objected, that in chemistry the term elasticity has a different meaning 

 from the one above given ; but if so, why has not Mr. Connon no- 

 ticed it in his appendix to the article on chemistry ? The fact is, how- 

 ever, that the term has, or ought to have, but one meaning, and in 

 the lessons on chemistry other words would certainly have conveyed 

 the author's meaning more distinctly. These defects, however, are 

 not serious ones, and we are of opinion that the lessons on chemistry 

 are amongst the most successful of the series : we heartily recom- 

 mend them to the attention of all young readers. 



Mr. Purcell's lessons on Mechanics are also well and clearly 

 written. 



Professor Tyndall's, on Natural Philosophy, are in every respect 

 admirable. The stj'le is attractive, lucid, and vigorous. The col- 



