286 Notices respecting New Books. 
matter, which follows, is mainly a record of the author's own 
brilliant researches in conjunction with Mr Soddy. The manner 
in which the author pierces the complexities of radio-active evolu- 
tion, and derives numerical results by deductive reasoning aided 
by the one sensitive methed of research, is more than admirable. 
Radio-active emanations are then treated. Here, again, the eluci- 
dation of the subject is mainly the author’s, and the discovery of 
these transitional bodies practically his own. Excited radio- 
activity, again the independent discovery of Professor Rutherford, 
is dealt with in the next chapter. Chapter X. brings us to the 
consummation of finding the author’s suggestion that in helium 
would be found a product of the material transformation of radium, 
verified in the experiments of Ramsay and Soddy. 
The book is throughout so full of suggestive facts that comment 
within bounds is difficult. That the existence of radium, as a 
constituent of the Earth, has swept away the argument which 
would limit the time required by the geologist, has been known 
since the correspondence in ‘ Nature’ of September and October 
last year. Professor Rutherford shows, however, in his book how 
completely the view that the Earth’s age is no longer determinable 
trom temperature gradient inwards, is justified. Geologists must 
now take for their time limits what interval denudation rates 
afford—whether measured by sedimentation or solvent denudation. 
With this subject is associated the origin of radium. It seems 
at present to be still quite unknown. In the work under notice 
preference is given to uranium as the source. Good reasons are 
given, but since then Mr. Soddy has shown in a letter to ‘ Nature’ 
that this source of derivation is very doubtful. May it not turn out 
that the escaped particles of the radio-active substances in pitch- 
blende are contributary to the formation of radium by intra-atomic 
combination with substances of lower atomic weight ? Perhaps this 
process goes further than the genesis of radium. There is an extra- 
ordinary richuess of elemental varieties in pitchblende. Radium 
happens to be a comparatively unstable atomic configura- 
tion, hence its distinction among the others. We are certainly 
obliged to seek for some source of supply of radium. The rapid 
rate of its destruction involves this. And, by the way, Professor 
Rutherford’s estimate of the rate of breakdown (p. 332) is even 
exceeded by the recent work of Ramsay and Soddy. 
We contess we do not care much for the term “ Conservation 
of Radio-activity.” We are accustomed to use the term “ Con- 
servation” in connexion with quantities such as energy, areas, 
matter. If we say radio-activity is subservient to the law of the 
conservation of energy and admit its intrinsic atomic nature, we 
do not see that anything is gained by the phrase introduced by 
the author and Mr. Soddy. 
We would like to see the table on p. 326 presented also in 
diagrammatic form. 
