866 



SCIENCE 



[N. S. Vol. XXIX. No. 752 



in radioactivity, and, moreover, the precise 

 measuremental matching of the lines of the 

 radio-elements vpith celestial lines is uni- 

 ■versally held to be essential to their identifica- 

 tion in the heavenly bodies. In direct viola- 

 tion of these vievps, radioaction, hypothesis a, 

 was proposed and confirmed. A second prin- 

 ciple, hypothesis ji, which need not now be 

 ■described, was also used from the first, and 

 thence a set of principles of interpretation of 

 celestial phenomena, deduced and verified, 

 which, for brevity, I designate the theory of 

 radioaction. 



The theory was originally verified with diffi- 

 culty by constantly summoning the calculus 

 of probabilities to its aid, and kept from pub- 

 lication on account of obstacles encountered 

 in presenting the vast mass of evidence. 



Eadioaction, or critical radioactivity, I 

 have used the last five years, as a principle 

 explanatory of many strange and hitherto 

 inexplicable phenomena, of inorganic evolu- 

 tion. I have found radioaction to be an 

 essential factor in cosmic evolution. By 

 means of it I have been able to predict the 

 necessary character of many phenomena pe- 

 culiar to the moi-phology, photometry, spectro- 

 scopy and electro-optics of nebulsB, stars, sun 

 and comets. Excepting two papers on this 

 subject, read before the American Philosoph- 

 ical Society, one, " Universal Celestial Radio- 

 activity," January 20, 1905, and the other, 

 " Eadioactivity in Solar Phenomena," April 

 14, 1905, both as yet unprinted, I have con- 

 tented myself, of necessity, with the accumula- 

 tion of proofs of the theory, until its presenta- 

 tion to the public in the form desired should 

 be feasible. 



Lately, however, the data for direct con- 

 firmation of this theory have come so freely 

 to hand that I have decided to lay aside, in 

 part, the ideal of aiming to present, as a unit, 

 my theory of radioaction, with all its wide 

 ramifications and interesting consequences. 



Eecently Mr. A. T. Cameron and Sir Will- 

 iam Ramsay have remeasured the spectrum of 

 radium emanation, and Professor E. Ruther- 

 ford and Mr. T. Eoyds have also brought to 

 bear all the refinements of physical accuracy 

 upon the same problem; so that now there is 



available a body of information of the highest 

 value concerning this spectrum. 



Reflecting upon the use of this material, my 

 theory suggested an investigation which re- 

 sulted in a very simple and decisive confirma- 

 tion of radioaction. This first and peculiar 

 confirmation, due to the later determinations 

 of the spectrum of radium emanation, I re- 

 serve for appropriate publication. 



It was on April 26 of this year that I 

 received Lick Observatory Bulletin, No. 149, 

 recording the work of Dr. E. A. Path on the 

 " Spectra of Some Spiral Nebulas and Glob- 

 ular Star. Clusters." This bulletin permitted 

 me, at once, to establish the fact that the 

 absorption spectrum of radium emanation was 

 present in this great nebula of Andromeda, 

 and in other spiral nebulse, and likewise pres- 

 ent in the star cluster of Hercules (probably 

 along with one line of radium), and in two 

 other star clusters. It also came out clearly 

 that the radium series of elements was not 

 disclosed by the spectrum of the Spiral Nebula 

 N. G. C. 1068. Finally, on referring to the 

 observations of hright lines in the nebula of 

 Andromeda by Sir William Huggins and Lady 

 Huggins, I was gratified, but not surprised, to 

 find that these lines were plainly identifiable 

 as lines of radium emanation. 



It has seemed proper to attempt here only a 

 brief examination of the facts, since the pres- 

 ent conditions prohibit a completely tabulated 

 and detailed discussion. Eirst, I must say 

 that it is with no little satisfaction that I find 

 myself reviewing this piece of superb work 

 issued under the direction of Professor Camp- 

 bell. Eor, in my study of radioaction, during 

 these five trying years, I have again and again 

 noted Professor Campbell's accurate and pains- 

 taking description of unusual celestial phe- 

 nomena, his balanced review of the work of 

 others (including the celebrated thrust con- 

 cerning the Purkinje phenomenon), and his 

 remarkable insight into the value of anomalous 

 observations, and of mooted suggestions for 

 their explanation. 



The telescope used by Dr. Eath in the work 

 was the celebrated Crossley reflector, with a 

 specially designed spectrograph attached. The 

 difficulties mastered were of the first order. 



