Dr Turner's Elements of Chemistry. 341 



In the second part he has treated of inorganic chemistry. The first sec- 

 tion of this part is on affinity. In discussing this subject the author admits 

 with Berthollet, that the result of chemical action is not always solely de- 

 termined by affinity. He proves that the order in which substances decom- 

 pose one another, cannot in every case be ascribed to the agency of chemical 

 attraction. He points out the mode by which cohesion, elasticity, and the 

 like, may act as modifying causes ; but, at the same time, contends that 

 Berthollet, in denying the existence of elective affinity, pushed his favour- 

 ite doctrine further than is justified by observation. 



In the following section Dr Turner treats of the proportions in which 

 bodies unite, and on the laws of combination, of the atomic theory of Mr 

 Dalton, of Gay Lussac's theory of volumes, and of the atomic views of 

 Berzelius. Without entering upon a detail of this extensive department, 

 we may give our readers an idea of the manner in which it is treated by 

 the following quotation. In commencing an account of the atomic theory, 

 Dr Turner observes, " The brief sketch which has been given of the laws 

 of combination will, I trust, serve to set the importance of this department 

 of chemical science in its true light. It is founded, as will have been seen, 

 on experiment alone, and the laws which have been stated are the pure 

 expression of fact. It is not necessarily connected with any speculation, 

 and may be kept wholly free from it." 



ff The reason why persons, partially acquainted with the subject, have 

 supposed it to be of a hypothetical nature, is sufficiently obvious. It was 

 impossible to reflect on the regularity and constancy with which bodies obey 

 the laws of proportion, without speculating about the cause of that regu- 

 larity ; and consequently the facts themselves were no sooner noticed than 

 an attempt was made to explain them. Accordingly when Mr Dalton pub- 

 lished his discovery of these laws, heat once incorporated his description of 

 them with his notion of their physical cause ; and even expressed the former 

 in language suggested by the latter. Since that period, though several Bri- 

 tish chemists of eminence, and in particular Dr Wollaston and Sir H. Davy 

 have recommended and practised an opposite course, both subjects have 

 been but too commonly comprised under the name of atomic theory ; and 

 hence it has often happened that beginners have rejected the whole as hy- 

 pothetical, because they could not satisfactorily distinguish between what 

 was founded on fact, and what was conjectural. All such perplexity would 

 have been avoided, and this department of the science far better under- 

 stood, had the discussion concerning the atomic constitution of bodies been 

 always kept distinct from what it was intended to explain. When employ- 

 ed in this limited sense, the atomic theory may be discussed in a few 

 words." 



The individual chemical substances are divided into the metallic and 

 non-metallic. They are not arranged according to any particular theory, 

 but are described in the order which the author conceives to be most con- 

 venient for the purpose of instruction. The only circumstance which we 

 s.-iall particularize in this department, is the mode of giving the tests. Dr 

 Turner states, that they are such as he employs in his own practice. The 



