40 



NATURE 



[March 9, 191 1 



trrritiiKMit, and nnmonclrituro, rind is fvidfntly de- 

 sij4n<'<l toe tlic use ot -ludt-iiK in in.nuial ir.iinini; lii^li 

 si'liools. One (il tlic (il)jc(t^, \\ (■ arc IdM, i-> li> ((ir- 

 rclatc the woiiv ol ihf inailiciualiral cla^Mcxjiii uilli 

 ihal of llic dcparlnicnls of mechanic arts and st'ifncc. 

 I"'or t\ani])lc, a studciil is licj^inninj^ to handii- hoards 

 in tiie shop and at the same lime is (dinuicncinj^ the 

 studv of almchra ; it is ad\ised that lie be assigned 

 some ])! ohitiiis on l)oai-d measure, together with a 

 review of uorii in fractions. It is, without doubt, 

 advisable to have a general workinj^ arrangement 

 between the mathematical classroom and the applied 

 science departments, but the arrarfg'ement, in our 

 (^l)inion, may be, and often is, carried too far. There 

 is a dani^er, if the connection be too intimate, of the 

 studen! sfxrialisins^ on his own account by giving 

 his earnest attention to those portions of the mathe- 

 matical woric wliich are adapted to fit the trade he 

 intends following, and giving scant attention to the 

 other portions. It is rarely the case that books of 

 the nature before us succeed in becoming an integra' 

 part of an effective educational system, despite the 

 fact that th(n- may be, as this one is, clearly written, 

 full of useful information, and well arranged. 



There are a few slips ; thus on p. 107 appears an 

 exercise on the work done while punching a hole. 

 It is impossible to work this problem without an auto- 

 graphic record of the operaition, although no hint of 

 this is given. Many teachers in trade schools in this 

 country will be glad to inform themselves of American 

 methods through the medium of this book, despite 

 the fact that they may find difficulty in placing it in 

 their pupils' hands owing to the nomenclature, to 

 which reference has been made. 



SPECTROSCOPY. 

 Haudbiich der Spectroscopic. Bv Prof. H. Kayser. 



Fiinfter Band. Pp. vi + 853 + TafeI ii. (Leipzig: 



S. Hirzel, 1910.) Price 48 marks. 

 A S is well known, Prof. Kayser planned to finish 

 ■^ *• his great handbook in four volumes, but owing 

 to the mass of the material dealing with absorption 

 the third volume was divided into two. The same 

 trouble has arisen over the fourth volume on the 

 original scheme, and the present volume contains only 

 the spectra of the elements, arranged in alphabetical 

 order, down to and including nitrogen. The sixth 

 volume, which is to appear shortly, will contain the 

 spectra of the remaining elements, and will conclude 

 the physical spectroscopy. 



As Prof. Kayser points out in his introduction, it 

 would have been very satisfactory to include under 

 each individual element a complete account of the 

 work that has been carried out on its spectra under 

 varying conditions of illumination. This would have 

 entailed, however, the expansion of the book by 

 several volumes, and therefore the details that are 

 given have been limited. In the case of the fifty 

 elements dealt with in the present volume, tables of 

 the wave-lengths of the lines in the arc and spark 

 spectra are given, and there also appears an account 

 of the work that has been carried out upon these 

 spectra of each element. Although this has of neces- 

 NO. 2158, VOL. 86} 



sity to be hrief, yet Prof. Kayser has dealt with the 

 \'ai"ious iini-sii^atioiis jn .1 nalical manner. In one 

 or two casts is ihjs .-ijct i;ill\ i.i l.c remarked, and 

 the articii- i)n tin- spccira ol carhoii si.inds out par- 

 tic ularlx as a tirn- crilical ri-\ii'\\, of ihc mam contribu- 

 tions to llic lih'ramrc of the suhji-rt. 



One great diffieLili\ faci-s ainonc who ;ittemj)ts i.> 

 collate the various nHasureimnis of the spectra of 

 substances, .and tiiat is ihc qm sii^ii of the standards' 

 upon whieti these mcisurt-mcnts .irr based. .As is 

 well known, fi>r the eii^hi \tars hiiwct-n 1885 and 

 iSq^, the standard generali\- emplo\fd was that of 

 .Angstrom's m.a[) as eornetcd \>\ Tiiait'n ; this was 

 superseded by Rowland's normal solar spectrum, which 

 differed from the previous one in an irregular manner. 

 Later it was sliown by Prof. Kayser himself that the 

 coincidence nn tliod used by Rowland with his con- 

 cave gratings is nut to be depended upon, and this was 

 borne out by Fabry and Perot, who proved by their 

 celebrated series of interference measurem -nis that 

 the Rowland scale is also irregular in its accuracy. 

 As a result of the discussion held at ilie meeting of 

 the International Union for .Solar Research, a ni w 

 standard has been set up by Fabry and Huiss,)n. 

 based upon the interferential comparison of a number 

 of equidistant lines with the Michelson cadmium 

 standard. This, however, is too recent to have had 

 verv much influence on comparative measurements. 

 As a result of the fact that the three standards are 

 not capable of accurate comparison, it is easy to see 

 that verv great accuracy cannot at jaresent be claimed 

 for manv of the published spectroscopic measurements. 

 Prof. Kavser remarks that the accuracy cannot be 

 depended upon to within o"i tenth-metre. 



Another difficulty that is met with in collating emis- 

 sion spectra is the relative intensity of the lines. It 

 is manifest that it is next to impossible to standardise 

 these intensities, for they vary so much with the 

 method of excitation and also with the sensibility 

 curve of the photographic plate. Different experi- 

 menters, moreover, have used different scales to which 

 the intensities are referred. The values given there- 

 fore can only be taken as a general guide to the 

 brightness of the lines, and cannot be considered of 

 much value in comparing the spectra of different 

 elements. 



There is no doubt that this volume is a very worthy 

 follower of the first four in the series, and must prove 

 an indispensable addition to the library of everyone 

 interested in emission spectra. Above all, it shows 

 the directions in which work, and that most important 

 work, still remains to be done. E. C. C. B. 



OVR BOOK SHELF. 



Subconscious PJiouuucna. By Hugo Miinsterberg, 

 and others. Pp. 141. (London : Rebman, Ltd., 

 n.d.) Price 5s. net. 

 P'oR the purpose of arriving at some unanimity, i 

 possible, on subjects regarding which there exists 3| 

 certain amount of diversity of opinion it has recentljr^ 

 become the fashion among psychologists to write a 

 symposiiitn in which each contributor gives expression 

 to his views. The present work, produced under the 

 editorship of Dr. Morton Prince, is of this nature and 



