464 



SCIENCE 



[N. S. Vol. XLIII. No. 1109 



vation is the leastj it unavoidably follows that 

 those left behind to continue the race, are those in 

 whom the power of self-preservation is the great- 

 est — are the select of their generation. 



Concerning this passage Spencer says in his 

 " Autobiography," p. 451 : 



It seems strange that, having long entertained a 

 belief in the development of species through the 

 operation of natural causes, I should have failed 

 to see that the truth indicated in the above- 

 quoted passages, must hold, not of mankind only, 

 but of all animals; and must everywhere be work- 

 ing changes among them. 



He attributes his blindness to his belief that 

 the inheritance of functionally produced modi- 

 fications suffice to explain evolution, and to the 

 further fact that he knew little or nothing 

 about the phenomena of variation. 



The great merit of Darwin is, of course, not 

 in originating the idea of natural selection, 

 but in so presenting it to the world that it 

 won acceptance. The fact that others antici- 

 pated him so far as the idea is concerned, does 

 not, of course, detract from his merit. Wal- 

 lace is entitled to much credit for the inde- 

 pendent discovery of the idea and its clear 

 presentation, but his anticipation was only in 

 the disposition to proclaim the discovery. The 

 foundation of Darwin's immortality is the 

 book, " The Origin of Species." He was per- 

 haps the only man in the world at the time 

 who could have written that book. We might 

 have attributed the possibility to Wallace, but 

 with a self-abnegation perhaps unparalleled 

 in the history of science, he said : 



I have felt all my life and I still feel, the most 

 sincere satisfaction that Mr. Darwin had been at 

 work long before me, and that it was not left for 

 me to attempt to write "The Origin of Species." 

 I have long since measured my own strength and 

 know well that it would be quite unequal to that 

 task. For abler men than myself may confess, that 

 they have not that untiring patience in accumu- 

 lating, and that wonderful skill in using, large 

 masses of facts of the most varied kind, that wide 

 and accurate physiological knowledge, that acute- 

 ness in devising and skill in carrying out experi- 

 ments, and that admirable style of composition, at 

 once clear, persuasive and judicial, qualities which 

 in their harmonious combination mark out Mr. 



Darwin as the man, perhaps of all men now liv- 

 ing, best fitted for the great work he has under- 

 taken and aceomplished.3 



i. w. howeeth 



Univeesitt op California 



the atomic weight of radium emanation 



(NITON) 



In the International Atomic Weights Table 

 for 1916,1 -jiig commission has adopted for 

 radium the value of 226.0, obtained by Hoenig- 

 schmid in 1911.^ The atomic weight of 

 radium emanation (niton), however, has been 

 retained at its former value of 222.1^ instead 

 of substituting 222.0, which would conform 

 with the new value for radium. The prob- 

 ability of an oversight in publishing the table 

 is perhaps eliminated by the appearance of the 

 same value in the German report.^ 



The retention of the value 222.1f raises a 

 question of considerable interest. The genetic 

 relationship among elements, and the conse- 

 quent interdependence of the atomic weights 

 of radioactive elements is relatively new, and 

 has as yet been given only indirect recognition 

 in the atomic weight tables (see below). Of 

 the 30-odd new radioactive elements, only 

 radium and radium emanation have as yet 

 been placed in the atomic weight table, since 

 they are the only two which could as yet be 

 obtained in sufficient quantity and purity for 

 the application of ordinary methods of atomic 

 weight determination. 



Since no new experimental work has ap- 

 peared on the atomic weight of niton, the 

 retention of its old value until such work ap- 

 pears might be regarded a priori as justified. 

 But it should be recalled that the experi- 

 mental work of Gray and Eamsay,* on which 

 the value 222.Ji. was based, in reality served 

 only to demonstrate the order of magnitude 

 of the atomic weight and would fit the value 

 222.0 equally as well as 222.1f. The latter 



3 "Contributions to the Theory of Natural Se- 

 lection" (1871), preface, pp. iv, v. 



1 Jour. Am. Chem. Soc, 37, p. 2,451. 



^Sitzb. Wien AMd., 120, p. 1,617; Hid., 121, 

 p. 1,973 (1912). 



^Zeit. phys. Chem., 90, p. 720. 



iProc. Boyal Soc, Si A, p. 536. 



