354 Notices respecting New Boohs. 



Hence, after a steady state is readied, this case is ex- 

 perimentally undistinguishable from that considered by 

 Mr. Mitchell. What appears to be the primary parent 

 substance is certainly the most slowly decaying in the series, 

 but whether it is preceded by others or! more rapid disin- 

 tegration we are not able to tell. 



We may, if we choose, regard the relative frequency of 

 the several types and species of organisms or other material 

 components of an evoluting system, when a steady distri- 

 bution is reached, as a measure of their respective " fitness," 

 or adaptation to the existing conditions. From this point of 

 view any members of a radioactive series, for which n<m, 

 appear as aggregates wholly unadapted to present conditions, 

 or having a " fitness " zero. They would thus correspond to 

 the " extinct" species of biology. 



Yours faithfully, 

 New York, ALFRED J. LOTKA. 



May 30, 1911. 



XXXV. Notices respecting New Books. 



Bulletin of the Bureau of Standards. Washington Government 

 Printing Office, 1911. 7oh VII. Nos. 1 and 2. 



QEVEBAL important papers are contained in these two parts. 

 ^ Messrs. Waidner and Burgess discuss the Temperature scale 7 

 between 100° and 500° C. The authors have determined the 

 boiling-points of naphthaline and benzophenone on the tempe- 

 rature scale denned by the platinum resistance-thermometer cali- 

 brated in ice, steam, and sulphur vapour (444°-70 on the const, vol. 

 Nitrogen thermometer). These two vapours give B.P.'s of 218 o, 

 and 306° C. respectively on the Nitrogen scale to a probable 

 accuracy of one-tenth degree. Messrs. Nutting & Tugman detail 

 investigations on the Intensities of some H, Ar, and He lines in 

 relation to current and pressure, the observations being made in 

 Pliicker tubes. Mr. J . H. Dallinger records an elaborate investi- 

 gation on the temperature-coefficient of resistance of copper and 

 the circumstances which tend to influence it. 



In Part 2 Mr. W. W. Coblentz gives the results of experiments 

 on the reflecting power of various metals, chiefly those used in 

 electric lamps. The measurements were made in the cold, 

 emphasis being laid on the recent work of Hagen and Rubens, in 

 which it is shown that for wave-lengths less than 4/j. the optical 

 constants of metals vary slightly, if at all, with change in tempe- 

 rature, and this is the region of interest on the question of the 



