248 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Oct., 1904. 



REVIEWS OF BOOKS. 



Radio-Activity. — Three books have recently been published 

 on radio-activity and the properties of radium ; and of these 

 three, that written with the title of •' Kadio-Activity." by Pro- 

 fessor Rutherford. D.Sc. F.K.S. (Canibridi;e: University 

 Press), niav be taken as the standard work on the subject. To 

 Professor Rutherford more than to any other one person is 

 to be ascribed the proof of the disintegration theory of radium ; 

 and the demonstration that the rays and the emanations which 

 are characteristic of radio-active substances are merely 

 svmptoms of the decay of the elements. We use the word 

 ••"proof," though the proof is far from complete, and the in- 

 ferences which Professor Rutherford draws from the proper- 

 ties of the a, ,rf, and 7 rays of radium, or from the conversion 

 of the gaseous emanation of radium into helium, are still dis- 

 puted by many chemists. If the inferences which Professor 

 Rutherford draws are the right ones, then we should e.xpect 

 nearly all substances to be more or less radio-active. Pro- 

 fessor J.J. Thomson, at the recent meeting of the British 

 Association, declared that, in his opinion, they were so ; and 

 though Professors Elster and (jcitel, whose work in radio- 

 activity entitles them to the most respectful hearing, did not 

 accept all Professor Thomson's conclusions, it is hard to see 

 how they are to be refuted. As Sir Oliver Lodge has re- 

 marked, if we accept the electric theory of matter, then one 

 might almost say that there is no need to piove the radio- 

 activitv of ordinary matter, for the burden of proof should 

 rather lie on the shoulders of opponents of this view, who 

 must show that it is not. If we are then to take the most 

 generally-accepted view of the reasons for the phenomena of 

 radium, a view which is now accepted by one of the greatest 

 of the earlier sceptics. Lord Kelvin, we must allow the views 

 put forward in Professor Rutherford's" Radio-Activity" to be 

 the only ones that can endure the test of examination. They 

 are, in a nutshell, that all the phenomena of radium are caused 

 by the splitting up of the atoms of which radium is composed, 

 aid their dispersal as electrons, or as new combinations of 

 electrons. The alternative view that there was something in 

 the constitution of radium's molecules or atoms which enabled 

 it to draw supplies of euergv- from the surrounding ether, or 

 from some other unknown sources of energy, has been declared 

 by Sir William Ramsay to be supererogatory. ."^mong the 

 special features of the book arc the historical treatment of the 

 discovery of the various phenomena of radium : The heat 

 emission (MM. Curie and Labordel ; the 3 rays: Sir William 

 and Lady Muggins's spectroscopic researches; a discussion 

 of the possible origin of polonium ; and a full account of the 

 results obtained by Sir William Ramsay and Mr. Soddy in 

 the production of radium emanation from helium. 



Mr. Soddy's book, "Radio-Activity" (the "Electrician" 

 Publishing Company), bears to Professor Rutherford's larger 

 work much the same relation that Puckle's " Conic Sections," 

 which was sometimes called Puckle's •' Salmon," bore to Dr. 

 Salmon's classic volume. This, however, is hardly fair to Mr. 

 Frederick Soddy, who is an investigator of great brilliance 

 and a writer of uncommon clearness, modesty, and per- 

 spicuity. He describes in the most admirable way the experi- 

 ments in which he has been associated both with Rutherford 

 and Ramsay, and his book, while not as exhaustive as that of 

 his former colleague, puts in a concise form the speculations 

 and conclusions to which the experiments gave rise. There 

 is at the end of his book a chapter called " Anticipations," 

 which in its title, if not in its subject matter, is perhaps 

 a little rash, but, as Professor Horace Lamb has said, •'even 

 in mathematics something must be risked." and Mr. Soddy's 

 speculations on the vistas of theory opened to our eyes by 

 radium are interesting to the point of enthralment. 



The third book which we have to include under this notice 

 is " Radium," by Leonard A. Levy and Herbert J. Willis 

 (Percival Miirshall and Co.); l>ut in so including it we are 

 bound to confess that w-e do it something more than justice. 

 It is not a text-book, nor yet is it quite a popular work in the 

 style of " Kadium-and-all-about-it," but is something between 

 the two. To those who wish to get a gener.d vit-w of radium's 

 properties, sufficiently accurate, and not at all heavy in com- 

 position, we may recommend it as a preparation for more 

 substantial works. 



The History of Painting in Italy. — The full title of Crowe and 

 Cavalcasselle's incomparable work, the first two volumes of 

 which have just been re-published by Mr. John Murray, and 

 the remaining four of which, edited by Langton Douglas and 

 the late Arthur Strong, are to follow in due course, runs " A 

 History of Painting in Italy. Umbria, Florence, and Siena, 

 from the Second to the Sixteenth Century." But the substi- 

 tution of one substantive for another is justified by the fact 

 that the history which Sir Joseph Crowe was assisted by 

 Signor Cavalcasselle to compile, remains now. as it was then, 

 distinctively and unalterably the history of the evolution of 

 the painter's art in Italy. As Mr. Langton Douglas incontro- 

 vcrtibly remarks, notwithstanding all that has been done in 

 the last forty years, by archivists on the one hand, and by 

 connoisseurs on the other, with the object of elucidating the 

 history of the central Italian Schools, this book continues to be 

 the standard authority upon the subject. It is in one sense 

 more than that. It is one of the few books of scientifically 

 accumulated facts, of which it might be said that an English 

 work is the admitted European authority. In the collection 

 of " co-efficients " on which to base theories the Germans are 

 apt to beat us. This work has all the laboriousness of German 

 effort without any of the repellent appearance of it ; it is, in 

 short, a work of art as well as a monument of human learning. 

 It is encumbered with few of those theories which are ac- 

 counted precious in one generation only to be forgotten in the 

 next ; but to the student who considers art from the point of 

 view of its evolution, it presents all the raw materials for 

 theory. If ever there should arise some Darwin among the 

 historians of painting — which perhaps the painters might pray 

 heaven to forbid — he would find no other work than this by 

 which he might trace the gradual evolution of a style or a 

 method ; the tendency to variability could be illustrated from 

 these pages ; the mutations arising from the accident of 

 genius could be dated and their influence assigned. This is. 

 however, to let one's imagination run away with one to an 

 extent that would have been severely discountenanced by the 

 authors, whose practice it was to admit no fact that had not 

 borne the test of the severest scientific questioning ; and we 

 iiiav fitly conclude this notice of a famous book by the state- 

 ment of the necessary facts concerning the new edition. The 

 original edition, now quite out of print, and very rarely to be 

 bought, and only at a great price, was enriched with few illustra- 

 tions. Its unique exactness and comprehensiveness was its 

 sufficing recommendation. Thenew volumes are illustrated with 

 all the resources of modern photography. Sir Joseph Crowe's 

 additions to the first four volumes, amounting almost to re- 

 writing, have been incorporated ; and to the original text 

 most valuable notes by Mr. Langton Douglas and Mr. Strong 

 have been added in smaller type. The first two volumes are 

 "Early Christian Art" and " Giotto and the Giottesques." 

 The Sienese School, the Florentines of the Quattrocento 

 and Cinquecento and the later Sienese and Umbrians will 

 follow. 



The Classification of Flowering Plants. — Dr. Albert Rendle's 

 task in the latest volume of the Cambridge Biological Series, 

 "The Classification of Flowering Plants " (Cambridge Univer- 

 sity Press), is to present to the student the considered results 

 in classification which are afi'orded by the latest research in 

 systematic botany. This, the first volume, deals with the 

 Gymnosperms. pines, cedars, spruces, &c., and with the 

 Monocotyledons, the lilies, grasses, and palms. The Dicotyle- 

 dons will appear in the second volume. Historically, the 

 general introduction is of the greatest interest, for here is to 

 be found a clear comparative summary of the successive 

 schemesin which Luin;Eus,Jussieu,andthe DeCandolles sought 

 to express the resemblances and relationships of the flowering 

 plants. Dr. Rendle has done something more than present 

 summaries of these classifications; his method of presenting 

 them is an essay in comparative criticism. In the rest of the 

 book Dr. Rendle adheres to the most generally-accepted 

 models of classification. That of the Gymnosperms includes 

 the latest palarontological discoveries of Drs. D. H. Scott and 

 Oliver. In discussing the Monocotyledons, the arrangement 

 of Dr. Engler is the one to which he adheres. There may be 

 some difference of opinion in respect of the nomenclature 

 adopted in the classification of the Monocotyledons; but of 

 the value of the work as a standard text book there can be but 

 one opinion. It is extremely well illustrated. 



