Notices respecting New Books. 239 



values are as follows (cf. Rudorf, Ann. d. Physih, xxix. 



p. 751 (1909)) :— 



81 



85 



86 



87 



88 



89 



90 || 



13-45 



13-19 



12-93 



12-68 



12-42 



12-17 



11-91 [I 



As regards <r, the best values for the monatomic gases are, 

 undoubtedly, those of S. Chapman (Phil. Trans, ccxvi. p. 279 

 (1916)), who found for argon <r=2'84xl0- 8 cm. Using 

 these corrected values for 7 and a 



Z^ -T=302 cals. 



On the other hand, L; is almost certainly more than 1284 

 [cf. Nernst, Ztschr. f. Elehrocliem. xxii. p. 185 (1916)) and 



approximately 1440, whence ,, i =240. The agreement 



o 



between 302 and 240 can hardly be considered good. 



Yours faithfully, 

 52 Cranley Gardens, G. RuDORF. 



Muswell Hill, N. 10. 

 5.11.19. 



XXIV. Notices respecting New Books. 



The Earth's Axes and Triangulation. By J. de Geaaf Hunter, 

 M.A., Mathematical Adviser to the Survey of India. (Survey 

 of India Professional Paper No. 16. ) Pp.viii + 219, with 6 charts. 

 [Printed at the Office of the Trigonometrical Survey : Dehra 

 Dun, 1918. Price Es. 4 or 5s. 4eJ.] 



HPHE first triangulation series of the Survey of India was com- 

 -*- menced as long ago as 1831. At that time, the best values for 

 the lengths of the axes and for the ellipticity of the earth were those 

 derived by Everest. Consequently the observations were reduced 

 using Everest's data as a basis, and in order to avoid discon- 

 tinuities, subsequent triangulation series have been reduced using 

 the same data, although it has for long been known that Everest's 

 values are substantially in error. Moreover, the values used for 

 the latitude and azimuth of Kalianpur, the origin of the survey, 

 have also been found to be in error owing to a considerable local 

 deflexion of the plumb-line. The necessity for freeing the results 

 from the errors due to these incorrect data has become more and 

 more pressing. To recompute the whole triangulation was of 

 course entirely out of the question ; the labour involved would 



