578 



NA'i (/</■: 



[( )< 1« >lil-.l< 20, 1923 



rcvi<vv This is ;i hold dt'sitrn. It is all the LTcattr 



j)l, i lli.it ihr Ihi. 



uii(|ii.ililii M iiiMi iiAcr, 1h ,11 1 il'. >.'. ! li (jiuc, 



[or it |)rii\ i.i I iin ,ii int riiihn Unii tn iiiudcrn 



atomic ■,))(•( iil;itinn> ulli' li >lioulil he in tlic !i:Ul(l> III 

 evciA >tuiliiit, ;um1 I an lie read u'itli ])rntit li\ iiiosi tc- 

 sean licr^. >\u\\ a hook lias until now not Ixcii a\ail- 

 ahlc 111 l'',iiL;!i>ti. and the want is scarcely lillid li\ tin- 

 re<tnt li.iii>lation of Sommcrfold's classir work, whu h 

 is r.ulirr loo loiii; and c-hilioratc and Muncwliat too 

 one-sided (spectroscopic) to be ( min l\ snital)|c in tliis 

 connexion. 



'J'o I'oinc to details. The i)ook i^ di\Hli-d into lu'o 

 parts (le,ilin_; with the existence and [irojierties of the 

 nucleus and with the extra-nuclear >trnitnre respec- 

 tively. In I'ail 1. altera shuit hi>toiir,il intnuhiction, 

 the first evidence for the exceedingly open structure of 

 the atom is presented in detail, as derived from the 

 passage of swift corpuscles through matter. An 

 important feature is the account of the work of Lenard 

 on the absorption of swift cathode ra) s, nuw too often 

 overlooked, which started atomic speculation on its 

 present path. There follows an excellent account of 

 the work of Rutherford in estabhshing the nuclear 

 structure, with its extensions by his school, and then the 

 radioactive evidence, including the recent work of Ellis 

 on the photoelectric effect and the interesting specula- 

 tions of Meitner. There is next a discussion of the 

 modern work on very close collisions between a-particles 

 and light nuclei — artificial disinteuiaiions by Ruther- 

 ford, and the deviations from the law of inverse squares. 

 A chapter on positive rays, with Aston's law of integral 

 atomic masses, concludes the nuclear evidence. In this 

 chapter there is one of the few questionable omissions. 

 In a paragraph on the separation of isotopes, Harkins's 

 work on hydrogen chloride is alluded to, but there is 

 no mention of the very elegant work of Bronstead and 

 Hevesy on mercury. 



Part I. then concludes with a critical account of 

 such theory of the nucleus as is yet possible, and two 

 short but necessary digressions, one on X-rays from the 

 classical point of view, and the other on the general 

 empirical laws of optical spectra. Both are good, but 

 exception can be taken to smaller points in the optical 

 chapter. To emphasise the fact that the majority of 

 known atomic spectra have not yet been ordered into 

 series is to overlook the fact that the time is still short 

 during which there has been a real theoretical incentive 

 so to order a difficult spectrum. But the yearly output 

 of such spectra at least partially ordered in series is now 

 considerable. Again, it is unfortunate that it has been 

 stated that atoms in general emit two optical spectra, 

 when we now have Al III and Si IV. But this, no 

 doubt, like the statement, already partly untrue, that 



NO. 2816, VOL. 112] 



there is no detailed theoretical foundation for optieal 



• ru and Kit/, i- 1 \ id'ie ■ 

 rallieroi the present raU: ol j^rcjgress than of inade(jua< i' 

 in the book. The t;eneral theorv of th< ^< term for!:: 

 wa> anni'un' 1 il 1 1\ Ij.ihr at ihi- ; 

 Ilrit i^li ,\s.->oi ialion. 



I'art II., on thee.M . m -.triK tur<-, starts with t .-. 



loHL' I ha|)tcr-. on the d\ i:aini< .d ini-d' 1 'A .itum 

 and more than one ■ ' ' ( lear a ' • . mese 



are till- least satis! tpters ir: k ; we 



return to thi ir . ■y are 



followed li\',iionii~ NMu 'II ,11,11 ijjeory 



ot atoinii .^trneture. wliirh ( onid ;- l)cttered in 



minor [mmt-. Th- of binding 



compared im orhit^ , ,.,. . .,,;>.,.! numl>er in 



hydroLien > muM he maih- . li ,irrr |.\ .m explicit definition 

 and use of " the effective quantum number " of the 

 external Keplerian loop of the orbit and its relation ti. 

 the actual total (|uantum nurnher. Again, n^ 

 distinction is made hetwt en the true relativity effect on 

 a Keplerian mhit and the similar effect due to (le\iation> 

 in the lau ir.iin the in\erse scju.;: 



occur in pra>M, i irom the \ariahle screening. Fmully 

 it is stated in error that the fifth and sixth electrons are 

 bound in 2^ and the thirteenth and fourteenth in 3, 

 orbits — a statement contradicted by the relevant table 

 on page 224. The error repeats an early statement by 

 Bohr, which he has superseded by thi> table. 



FollowinLT this there is an excellent s)-mpathetic 

 account ot static models of the atom and their value 

 in organising the facts of chemistry. This chapter 

 makes it clear in an intercstinci wav that though all 

 attempts to make .static models with any natural 

 physical reality are a waste of time, such models, like 

 the elastic spheres of the kinetic theory, have a large 

 legitimate "place in the sun." The book concludes 

 with what should pnn-e a \"ery useful survey of the 

 present chaotic state of mai^netic theory. 



To return to the chapters on the dNTiamical atom. 

 The re^'iewer would make the general criticism that they 

 present the >utiject from a point of \iew which, without 

 prejudice, may he called too " Sommerfeldian." With- 

 out in any way belittling Sommcrf eld's classical contri- 

 butions, it is the correspondence princiuli^ ;ind the 

 fundamental fretjuencies of the atom; Bohr's 



method of attack, and not the W il>. a-Sommerfeld 

 quantum conditions, which ought to he made funda- 

 mental. .dio\e ail in a hook for i)hysieists. " Ought '' is 

 the word, for reasons which the author of tins book has 

 himself formulated as clearly as possible, for this is the 

 method which seems to w..rk ix-t. and t(t he in closest 

 touch with physical reality. His prefator}- quotation 

 of Kelvin should be re-quoted — " Nothing can be more 

 fatal to progress than a too confident reliance on mathe- 



