Notices respecting New Books. 285: 
and Matter’ is to feel we have gained anew cosmos; to expand in 
Richter-like flights among the galaxies of the “ indivisible ” material 
unit ! 
The general nature and occurrence of radio-activity and the 
subject of the ionization of gases occupies the first two chapters. 
J.J. Thomson’s great advance in finding the value of e, and hence of 
m, finds a place here. The ionization of gases is clearly treated in 
the brief space given toit. The succeeding chapter on Methods of 
Measurements will not only be valuable to those wishing to work 
in this field, but is requisite for the understanding of the extra- 
ordinary progress of research of which the book is a record. 
Rate methods, now almost exclusively used, alone are described. 
Chapter IV. records the evidence which has been advanced for 
the material nature of the alpha and beta radiations. Kaufmann’s 
experimental verification of the views of J. J. Thomson on the 
electrical origin of mass, using the formula of M. Abraham, 
is given here. On the subject of the spinthariscope we confess 
to some difficulty in seeing how it can be assumed on the evidence 
that the impact of each alpha ray is marked on the screen by a 
flash of light. The phenomenon, we take it, is similar to the 
light given out by sugar, &c., when crushed, and the irritation, 
mechanical or electrical, required to produce a cleavage might 
surely be as often due to the near coincidence of, say, ten collisions 
as the effect of one; if, indeed, we may assume that the impact of 
one ray is ordinarily adequate. When we have reached section 87 
of this important chapter we have developed the subject so far as 
to see in the alpha particle a freed constituent of the heavy atom 
of radium, having a mass about that of helium, which must 
be rotating within the radio-active atom with a velocity sufficiently 
enormous to account for the speed in virtue of which we 
recognize its existence; while the beta particles pour into 
space with a speed of motion about ten times as great, and 
strangely near the velocity of light. Reading further, we find 
that the nature of the gamma rays is by no means well deter- 
mined, although the weight of evidence assigns to them the 
character of very hard X-rays. The chapter concludes with an 
account of secondary rays, a subject possibly of considerable 
medical interest at no distant. date. These deviable rays, copiously 
produced by gamma radiation, may afford a means of application 
of radio-activity to deep-seated disease which will be yet under 
the control of the physician and may be remitted at his will. The 
presence of an inert heavy metal, such as gold or platinum, at the 
seat of injury being alone required. Surface trials of this secondary 
radiation are being made; as we write, in a Dublin hospital and not 
without promise of success. 
Measurements of the rate of emission of energy occupy the 
ensuing chapter. The author then briefly refers to the many 
strange effects of the radiations: phosphorescent; physiological, 
&c. The subject of the continuous production of radio-active: 
