Notices respecting New Boohs. 155 



Dr. Frankland is an upholder of the doctrine of varying valency. 

 In his paper on Notation he brings forward the unhappy example of 

 Ammonium Chloride as illustrative of compounds in which 

 Nitrogen is pentavalent : in Nitrous Oxide he says Nitrogen is 

 monovalent. Surely such statements as these are far too rash : 

 we do not know the molecular formula of sal ammoniac; and 

 we are much more justified in saying that nitrogen is trivalent in 

 nitrous oxide, than in averring, as our author does, that the same 

 element is trivalent in nitric oxide. Variation in valency seems to 

 take place by leaps : a trivalent element may, it seems, sometimes act 

 as monovalent, but rarely, if ever, as a divalent element. Such facts, 

 says Frankland, " can be explained by a very simple and obvious 

 assumption, viz. that one or more pair of bonds belonging to one 

 and the same atom of an element can unite, and, having saturated 

 each other, become, as it were, latent." We fail altogether to see 

 that this " simple assumption " explains the facts in any way ; it 

 merely restates them. On pp. 24, 25 there appears a most unfor- 

 tunate list of mineral compounds formulated in accordance with 

 Dr. Frankland's system. The formulae there given are pleasant 

 to the eye ; but that is all. For the most part they really have 

 no Jrnoivn foundation in fact. 



Section II. includes those papers which have been contributed 

 by Dr. Frankland to Applied Chemistry : these papers chiefly deal 

 with subjects connected with Gas and Water. The practical re- 

 sults of the work collected in this section are known to all. We 

 are certainly largely indebted to the author of these researches for 

 many improvements in our lighting and in our water-supply. The 

 memoirs now collected form a good example of the benefits which 

 always accrue when science is adequately applied to technical sub- 

 jects. They may furnish a powerful argument to those who are 

 ever urging Government to expend a larger portion of the nation's 

 money in investigations undertaken by really qualified scientific 

 men into those problems of applied science which every one 

 acknowledges must be solved, but which can only be solved by 

 national effort. 



The papers upon Water-analysis recall the controversy between 

 the upholders of the system of Wanklyn and those of the sys- 

 tem of Frankland. Such a controversy should never have oc- 

 curred : happily there are signs that the bitterness is dying away ; 

 let us hope that the action of time will be as the action of a flow- 

 ing river upon the subject which has engendered this hostility, 

 and that before long the clamour may be remembered only as a 

 dream of " previous sewage contamination." 



In the Third Section we are presented with the papers on Phy- 

 sical Chemistry contributed by Dr. Frankland to science : these 

 papers, for the most part, contain the record of work done or sug- 

 gested during holiday excursions. " The Influence of Pressure 

 upon Combustion," the " Spectra of Gases and Vapours," the 

 " Source of Muscular Power," and " Climate " form the main sub- 

 jects dealt with in this section. The results of Dr. Frankland's 

 researches in these various fields have passed into the common stock 



