November 7. 1918] 



NATURE 



183 



!\ of the monatomic gases witH no chemical 

 it) has made available elements which ap- 

 ich the "ideal gas" nearer than hydrogen or 

 nitrogen. Argon will probably be employed in 

 all the higher temperature gas thermometry be- 

 cause it does not dill use readily through quartz. 



In the chapter on the mercurial thermometer 

 some useful information is given as to the con- 

 struction of the electrically heated testing baths 

 now in use at tin- National Physical Laboratory; 

 indeed, one of the not least valuable features of 

 the I ! ionsi-.ts in the data and illustrations 



: ot tin thermometer and pyrometer testing 

 equipments of this laboratory. 



The chapters on the resistance thermometer and 

 the thermo-couple show that a great deal of ex- 

 perimental work has been devoted to developing 



the precision of the results obtained with these 

 instruments. It is to be regretted that tin- author 

 has not been able to deal more fully with their 

 commercial development. We notice the omission 

 of Peake's compensating leads and the very brief 

 mention of the modern recording instruments, 

 base metal thermo-couples. 



Four interesting chapters are devoted to the 



study of radiation and optical pyrometers and the 

 problems connected with them. From the scien- 

 tific, as well as from the industrial, point of view, 

 the measurement of very high temperatures is of 

 interest. The instruments in themselves 

 are comparatively simple, but the extrapolation 

 of their si alis beyond 1400 C. is a problem of 

 considerable difficulty. A large number of workers 

 will be grateful to Dr. Ezer Griffiths for the con- 

 ol the work on which this extra- 

 is based. 



In connection with the explanation of the 

 Wanner optical pyrometer, it should be pointed 

 out that the images of the illuminated patches are 

 circular (being images oi the circular diaphragm), 

 and not semi-circular, as stated. The description 

 of the instrument on p. 120 is not so accurately 

 worded as it should be. The diagram is not well 

 printed, and is thus difficult to understand. 



\ useful bibliography is given at the end of 

 chapter. \ small slip on p. 55 may be men- 

 tioned; for Tables xlix. and 1., xlvii. and xlviii. 

 should be substituted. 



'I he book is a useful, short summary of the 

 subject, and, although not so complete as one would 

 have desired, may be recommended as an addition 

 to the library of every physics laboratory. 



OUR BOOKSHELF. 



fur Parent.': and Trackers. By 

 Dr. T. W. Galloway. Pp. ra8. (London': 



I). C. Heath .and Co., n.i.].) Price 2S. net. 



Convinced of the need for sex-instruction, Dr. 

 Gallowaj seeks to givi parents and teachers some 

 idea of the biolog ethical principles which 



should underlie it, and to suggesl the spirit in 

 which it should be attempted. He has sympathy 

 with endeavouring by knowledge to avoid disaster, 

 but he sees positive promise in trying to use the 

 NO. 2558. VOL. I02] 



sex impulses and instincts cdueatively. He seeks 

 to present the facts of sex i„ their broad biological 

 and evolutionary setting, and the lines of instruc- 

 tion suggested seem to us to lie shrewd and wise, 

 lie would in a graduated and differential way 

 explain to young people that if their sex-develop- 

 ment goes awry, the results will show themselves 

 in reducing the efficiency of body and mind. "The 

 purpo.se of sex-knowledge is to enable you to let 

 yourself develop normally without giving the 

 matter tiny unnecessary thought." Hut the power 

 oi ontrol over impulses requires strengthening 

 even in the strongest, and the author writes in an 

 enced, practical way of the ideas and ideals, 

 habits and interrelations thai make it less difficult 

 to "keep the heart with till diligence." 



Emphasis is wisely laid on the importance of 

 grading the instruction according to intellectual 

 and emotional development and the diversity of 

 social and economic relations. The linking of sex- 

 instruction to biology and hygiene on one hand, 

 and to ethics and eugenics on the other, is a 

 good feature of a concise and clearly written book 

 which can be confidentlv recommended to parents 

 and teachers. Now and again we have come across 

 a sentence that jars (e.g. on p. 119: "Because of 

 this shell, chickens cannot behave like fish in 

 fertilising the egg"), but the workmanship of the 

 book is thoroughly competent. 



The Processes of History. By Prof. F. J. 

 Teggart. Pp. ix+162. (New Haven: Yale 

 University Press ; London : Humphrey Milford, 

 1918.) Price 5s. 6d. net. 

 The main argument of this essay is that historians 

 should take into account the natural processes 

 that have moulded human groups, and that the 

 history of no one area can be viewed indepen- 

 dently of that of its neighbours. A powerful plea 

 1 ; put forward for the recognition of a history of 

 Eurasia, in which Western events may be treated 

 a- the outcome of climatic and other incentives 

 to movement in the broad lands lying to the East. 

 The author urges that Lyellian methods cannot 

 be applied to history, though correct inferences 

 from historic data " should be verifiable by appli- 

 cation to things as they are." Our range of view, 

 in seeking for causes of human action, cannot be 

 restricted by epochs and localities, and the domi- 

 nance of mere narrative in history seems already 

 overthrown. Prof. Teggarl regards primitive man 

 as engaged in maintaining a system of life which 

 he has found sufficiently advantageous. In thus 

 minimising the influence of the gifted and ingeni- 

 ous member of the tribe, or of the hunter whose 

 adventurous outlook has brought him into open 

 country from the confining darkness of the woods, 

 he strikes a blow at the theory of leadership as 

 a cause of rapid change and evolution. Tribal 

 movements appear to him to originate in some 

 broad change of condition, and the migration thus 

 enforced by Nature leads to development by col- 

 lision with men who have followed other modes 

 of life. The book will perhaps be of service in 

 pointing out the problems rather than the methods 

 of modern history. G. \. J. C. 



