538 



NA TURE 



[September 27, 1906 



■" expounded with such wealth of illustration and with 

 so exhaustive a knowledge of the fundamental litera- 

 ture of the subject." This praise is, we think, fully 

 deserved. Dr. Meldrum brings stern logic to bear 

 on the question, and approaches his task with a grim 

 earnestness which imparts an unintentional tinge of 

 humour to his book. He is no respecter of persons, 

 and he handles with some severity all those who, in 

 his opinion, have been unfaithful to the facts. " The 

 atom," says Dr. Meldrum, " in the modern theory 

 of chemistry is a 'dependency of the molecule.'" 

 " Avogadro's hypothesis being the fundamental hypo- 

 thesis of chemistry, other doctrines concerning mole- 

 cules and atoms are to be subordinated to it." " The 

 atom can be defined with reference to the molecule ; 

 it is doubtful if any other definition is sufficient." 

 These quotations will perhaps suffice to indicate Dr. 

 Meldrum 's view. Dalton's hypothesis came first, but 

 since 1858, when Cannizzaro appeared on the scene, 

 Avogadro's hypothesis has been the fundamental one. 

 We do not think that this can be seriously contested, 

 taking the words strictly in the sense intended by 

 Dr. Meldrum. At the same time there is surely some 

 danger of a too pedantic insistence on this question 

 of " ratiocinative precedence." If we look upon the 

 progress of chemistry, and not merely on its present 

 state, it is hardly a crime to speak of that hypothesis 

 as fundamental which has been the immediate cause 

 of another that has ultimately proved more general, 

 comprehensive, and fruitful, and whilst no doubt there 

 has been some laxity on the part of chemical writers in 

 their choice of words, the great fact that Dalton came 

 first, and that without Dalton there is no reason to 

 suppose there would have been an Avogadro's hypo- 

 thesis, will still be regarded, we suspect, as a justifi- 

 cation for some of the statements which Dr. Meldrum 

 criticises so severely. 



In saying this we do not wish for a moment to 

 underestimate the service which Dr. Meldrum has 

 rendered by giving us this very searching and able 

 review of the bases of modern chemical theory. 



A. S. 



Die radioaktiven Siibstanzen ttnd die Theorie des 

 Atomzerfalles. By Prof. Paul Gruner. Pp. 103. 

 (Bern : A. Francke, 1906.) Price 1.60 marks. 

 This little book of 100 pages, we learn from the pre- 

 face, had its origin in courses of lectures delivered 

 by the author at the University of Berne during the 

 session 1904-5, and is designed to give a complete 

 yet short review of the whole field covered by the 

 title, including the most recent investigations. The 

 subject is presented from the point of view of the dis- 

 integration theory, and the phenomena connected with 

 the induced activity are treated at length. The 

 physiological action of radio-active substances, and 

 their existence in springs, &c., are not considered 

 except in passing. 



The author is to be congratulated on having. fully 

 carried out his intention, and has succeeded in pro- 

 ducing a very readable account of the subject from 

 the physical standpoint, which is thoroughly up to 

 date ; but the value of the work would have been 

 much enhanced by more diagrams. Only three are 

 included, illustrating the decay and growth curves of 

 the induced activity of radium, and not a single 

 diagram of any experimental piece of apparatus is 

 shown. Practically nothing is said of the methods 

 of measurement in use in the laboratory, although 

 perhaps this is as well in a subject of this kind, where 

 a little knowledge is apt to be a dangerous thing. 

 On the other hand, the author has contrived to com- 

 press within the one hundred pages of his book a 



NO. 1926, VOL. 74] 



surprising amount of the best of the most recent 

 literature, and this makes us venture to express the 

 hope that in a future edition the author will rely less 

 on the existing compilations in dealing with the 

 earlier researches, and will extend to the whole litera- 

 ture of the subject the same careful and first-hand 

 consideration he has shown in dealing with the latest ■ 

 researches. 



Of criticism or comment there is little or none, but 

 there is evidence of considerable skill in the selection 

 of the material whereby the most important researches 

 secure prominent treatment. With the exception of 

 the recent work emanating from Australia on the 

 a rays, of which perhaps the full bearing has not 

 been sufficiently brought out, the living branches of 

 the subject have been done full justice to. A refer- 

 ence to the parts dealing with the slow transformation 

 products of radium, radio-thorium, the origin and 

 ultimate product of radium, the work in Germany 

 and France on the production of helium from radium 

 and actinium, and radio-tellurium and polonium, 

 shows that the author has included the best of the 

 current work on the most important problems. 



F. S. 



Introduction to Astronomy. By Prof. Forest Ra} 



Moulton. Pp. xviii-l-557. (New York: The Mac- 



millan Company; London: Macmillan and Co., 



Ltd., 1906.) Price 5s. net. 

 Students of astronomy will find in Prof. Moulton 's 

 volume an excellent text-book which, by its luciditv 

 and wealth of detail, will enable them to obtain a 

 fairly thorough grasp of their subject. 



After two chapters dealing with general outlines 

 and definitions we find a very useful chapter on the 

 constellations, with special paragraphs on the more 

 important stellar groups and simple methods of 

 locating them. Four clearly printed maps, so bound 

 that thev open out flat when the book is opened, will 

 be found very useful in the practical work which here 

 and throughout the book is insisted upon as being 

 essential. 



Telescopes, their evolution and various types, are 

 then discussed, whilst the earth, its movements, 

 gravitation, and time are dealt with at some length 

 in the four succeeding chapters. 



Chapters ix. to xii. deal with the moon, eclipses, 

 the solar system as a whole and its individual 

 members, respectively. The chapter on comets and 

 meteors which follows leaves little, if anything at all, 

 to be said concerning the general phenomena and the 

 historical apparitions of these bodies. 



Probably in no branch of astronomy have such rapid 

 advances been made during recent years as in solar 

 physics, and of the results obtained therefrom Prof. 

 Moulton takes the fullest advantage in the forty-nine 

 pages of description and discussion which he devotes 

 to the sun in chapter xiv. Again, as a pioneer worker 

 on the probable evolution of the solar system, he is 

 seen to great advantage in the next chapter, where 

 he describes and criticises the Laplacian hypothesis, 

 explains the work of Sir George Darwin, and sum- 

 marises the theories advanced by Prof. Chamberlin 

 and himself. 



In the concluding chapter we have an epitome of 

 our present knowledge concerning " the stars and 

 nebulas," in which the facts and observations of most 

 branches of sidereal astronomv are clearly stated and 

 discussed. 



The numerous questions placed at the end of each 

 chapter and the excellent and up-to-date illustrations 

 add greatly to the value and interest of the volume 

 as a text-book. W. E. R. 



