292 
whether of the older or newer school, must per- 
force take into consideration. 
From this last point of view the present work 
presents certain special advantages which may be 
summed up by the statement that the author 
handles his subject as a chemist. The day has 
passed away when workers with parochial views 
of their science can hope to impose upon the 
present generation stupidly narrow limitations 
by “method ”—to insist that the evidence based 
upon “purely chemical” methods is alone of 
weight to chemists, and that the results achieved 
by “purely physical”? methods must be received 
with suspicion. But for the chemist it certainly 
is of importance, in view of the bewildering 
rapidity of the development in this newer domain, 
to have the results, by whatever method achieved, 
co-ordinated and fitted in to that older structure 
with which we were all familiar in the days of 
our own studentship. Dr. Letts may be con- 
gratulated upon having accomplished this task 
with conspicuous success within the compass of 
his brief. His historical records, which are fairly 
given, are as up-to-date as can reasonably be ex- 
pected, and the descriptive portions are sum- 
marised at the end of the chapters with a clear- 
ness which shows that the author has a thorough 
grasp of his subject. Perhaps it may be urged 
by extreme critics that he is not sufficiently 
critical—that he appears to accept as established 
truths and without comment published statements 
concerning “‘transmutation,” about which there 
is conflict of evidence. But the present work pro- 
fesses to be but a literary production, and the 
author, perhaps wisely in the present state of 
knowledge, simply sets forth the evidence and the 
suggested interpretations of that evidence. All 
who have watched the development of this “ newer 
chemistry ” have thoroughly realised the extra- 
ordinary practical difficulties which confront the 
experimenter at every stage. The infinitesimal 
quantities of material which have to be dealt with 
and the extreme delicacy of the methods of at- 
tacking the new problems offered by a subject 
which is still “in the making” are such as to 
give much scope for apparently conflicting evi- 
dence. The future writer of the history of chem- 
istry will find ample matter for marvel at the 
results which have even now been achieved in 
spite of the difficulties referred to. That Dr. 
Letts is himself appreciative of the skill which has 
surmounted so many of these obstacles is apparent 
in many pages of the volume under consideration. 
It is now a matter of ancient history that on the 
discovery of spectrum analysis chemistry and as- 
tronomy entered into partnership. But the new 
chemistry, as understood in the present work, has 
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NATURE. Vf 
| ary 
[May 21, 1914 
also widened the horizon of the science to an ex- 
tent that renders necessary the consideration by 
chemists of problems of a cosmical order in a 
much more definite and concrete form than has 
hitherto been customary. It is obvious that ques- 
tions concerning the constitution of the atom and 
the evolution or disintegration of matter cannot be 
confined within terrestrial limits. On the first of 
these questions the author has something to say, 
| and in the ninth chapter will be found a succinct 
account of the electron theory, with reference 
more especially to the work of J. J. Thomson. 
Now it is precisely on this question of the present 
position of the electron theory that chemists are 
awaiting further light from the physical side. So 
far, with the exception of Sir William Ramsay’s 
preliminary attempt, this theory cannot be said 
to have been brought seriously within the domain 
of practical chemical politics. It is not mere 
curiosity that prompts the chemist to ask whether 
the atom is to be regarded as a complex mechan- 
ism composed entirely of electrons or whether 
there may not be other components. Dr. Letts 
thus answers the question :— 
“From spectroscopic and other evidence it 
would appear to be certain that electrons are uni- 
versal constituents of atoms, but on the other 
hand, there appears to be no sufhcient evidence 
for the assumption that electrons are the sole con- 
stituents of these atoms. all but about one- 
thousandth of its mass is associated with the posi- 
tive part of an atom, which would tend to show 
that an altogether exaggerated réle has been at- 
tached to the electron in the constitution of 
matter.” 
This at any rate was the view held by the writer 
of the section on radioactivity in the Annual Re- 
ports of the Chemical Society in 1906, from whom 
the author takes his information. 
With reference to the other question—the evo- 
lution and dissolution of matter—the reader will 
find in the tenth chapter a good summary of the 
observations and conclusions of Lockyer, as set 
forth in his ‘Inorganic Evolution” and other 
publications. One result of the “new chemistry ” 
is thus to bring us back to what may be termed 
the presentation of the case from the astrophysical 
side. There is distinct evidence of this reaction- 
influence of the new chemistry upon the 
pioneering work of Lockyer now to be found in 
many recent treatises besides the volume under 
consideration, in which some twenty pages are 
devoted to the subject. The “disintegration” 
theory of radio-activity, which now holds the field, 
has brought into modern chemistry certain very 
concrete notions concerning what may be defined 
as down-grade evolution. It is but natural to 
ask with Dr. Letts (p. 190) whether the reverse 
