242 



NA TURE 



S^Jan. 12, I 



science arranged in logical sequence ; it is a guide to 

 the student and the investigator (for in chemistry these 

 two are one) ; and it is full of suggestions alike to the 

 physicist and the chemist. 



That part of the second volume which deals with the 

 recent developments of the study of chemical affinity will 

 probably be found by many to be the most interesting 

 portion of the book. Everyone knows how unsatisfactory 

 is the treatment of this subject in the standard text-books. 

 Who has not been perplexed as he attempted to gain 

 clear conceptions about affinity ? Affinity is one of those 

 terms that escape one as soon as one tries to grasp it : it 

 is protean, and each form which it assumes scarcely lasts 

 long enough for one to distinguish it from the others. 



The work of Guldberg and Waage, published twenty 

 years ago, did not bring forth much fruit for some time ; 

 perhaps because these naturalists were obliged to go back 

 sixty years to find in the writings of BerthoUet the germs 

 of a really exact treatment of the subject of affinity. But 

 within recent years great advances have been made — and 

 made, speaking broadly, on the lines laid down by the 

 Norwegian professors. No one has had more part in 

 these advances than Ostwald ; to him we are indebted 

 for several new experimental methods for finding values 

 for the affinity-constants of acids and bases — indeed the 

 proof of the existence of a measurable affinity-constant 

 for each acid and base is, for the most part, due to him. 

 It is one thing to know that memoirs are to be found in 

 the journals wherein the subject of affini:y is gradually 

 advanced stage by stage, but it is quite another t'ling to 

 have a clear, logically arranged, and condensed account 

 of these memoirs in a text-book. It is one thing to bs 

 told that the modern development of affinity is the out- 

 come of the views which BerthoUet published, in 1803, in 

 the Essai de Statiqiie Chimique ; it is quite another thing 

 to have this historical and logical development set before 

 one in detail in a masterly manner. 



The subject of affinity is largely involved in the wider 

 conception of chemical equilibrium. Ostwald gives a 

 short account of the attempts which have been made to 

 formulate the laws of chemical equilibrium. He then 

 narrows the meaning of affinity, at least as applied to 

 acids and bases ; by doing this it becomes possible to 

 extricate the notion of affinity from the mass of more or 

 less connected facts which had threatened to swamp it, 

 and to give it a quantitative meaning. 



The affinity-constants of acids and bases are numbers 

 which tell how much of a definite chemical action those 

 bodies are capable of performing under definite conditions. 

 The formulas of the same acids and bases exhibit the 

 composition of definite masses of these compounds, 

 which masses are in many respects chemically compar- 

 able. The goal of chemistry has always been to trace 

 definite connections between the composition of bodies 

 and their chemical properties ; but of all the chemical 

 properties of a body the most important is its affinity- 

 constant, inasmuch as we are apparently justified in 

 saying that this value quantitatively conditions all the 

 chemical reactions in which the body takes part : hence 

 the importance of accurately tracing the connections be- 

 tween the changes of compositions of bodies, as repre- 

 sented by their formulae, and the variations in the values 

 of the affinity-constants of these bodies, must be very 



great. Th ^ data are as yet insu.fficient to allow of more 

 than a beginning in this direction : such a beginning is 

 made in the last chapter of Ostwald's book. 



To everyone who hopes to make chemistry the business 

 of his life I would say— get Ostwald's " Lehrbuch," read 

 it, study it, become acquainted w'.th it, use it ; for by doing 

 this you must become more fitted for doing your work as 

 a chemist. M. M. Patti^on Muir. 



BRITISH AND IRISH SALMOMDJ:. 

 British an.i Irish Salnwnidcr. By Francis Day. 12 

 Plates. (London and Edinburgh : Williams and 

 Norgate, 1887.) 



IN this work Mr. Day expounds in greater detail the 

 views he made known in his " British and Irish 

 Fishes," concerning the characters and affinities of the 

 several British forms belonging to the genus Salmo. He 

 also includes in the volume the consideration of many 

 other important problems connected with the natural 

 history of British Salm^noids. On p. 9 he gives a 

 synopsis of the British genera of the family, viz. Salmo, 

 ThymiUus, Coregonus, Osmerus, and Argentina, and 

 then proceeds to con5ider Genus i, Salm-), while at p. 278, 

 is the heading Genus 2, ThymxUus, Cuvier. For the 

 designation of species and varieties English names are 

 generally used, but with each is given a copious list of 

 the Latin Linnean synonyms, and references to the 

 works where they occur. The species considered are as 

 follows : the Salm:)n, Trout, British Char, American 

 Char or Sabiu fontinalis, and the Grayling. Thus 

 Coregonus, Oimerus, and Argentina are left outside the 

 scope of the book, notwithstanding its comprehensive 

 title. 



Very elaborate descriptions, including enumerations 

 and dimensions, are detailed for each separate form^ but 

 concise diagn )suc analysis is entirely wanting. In the 

 synopsis of species of Salmo given in the earlier work, 

 "British and Irish Fishes," we find that the only trust- 

 worthy specific character differentiating Salmo salar from 

 Salmo trutta is the presence in the former of eleven rows of 

 scales in an oblique row from the adipose fin to the lateral 

 line, all forms of Salmo trutta having fourteen or more of 

 such scales. In the work before us one has to wade 

 through two pages and a half of description of the salmon 

 before reaching a mention of this diagnostic feature. 



The views here expressed concerning the forms of 

 sea-trout are somewhat different from those pub- 

 lished in the " British and Irish Fishes " In the 

 latter work Mr. Day described Salmo trutta and two 

 varieties, S. albics and S. camhricus. In the present 

 he describes Salmo albus (with the same synonymy) as 

 the immature stage or grilse of the northern sea race 

 of trout, S. cambricus being the southern sea race. Here 

 again the want of a short diagnosis of the two. races is 

 much felt by the reader. From the numerical formulse of 

 the two races, which are separated by several pages, it is 

 seen that the range of variation in the number of pyloric 

 caeca in the one race is different from that in the other. 

 In the northern form it is 33-61, in the southern 33-52. 

 But it is extremely difficult, by reading and comparing the 

 two lengthy descriptions, to discover what is the exact 

 amount of difference between the two races. However, 



