
_ Feprvary 17, 1923] 
NATURE 
215 

_orin the United States. The language next in evidence 
is French. 
___ The period covered—the second half of the war and 
_ the following year—was not very fruitful in scientific 
_ research, except in regard to subjects bearing upon the 
great conflict, but it is clear, both from the number 
_ of entries and from the number of journals consulted, 
that the index does not claim to be a complete record 
_ of all scientific and technical papers published during 
that period, but that a selection has been made. It 
would add to the value of these publications if the 
editors could see their way to include a list of the 
periodicals indexed in each section of these indexes 
when it is published. The inclusion of the name of 
a journal in such a list would not, of course, mean that 
all the papers printed in that journal had been indexed, 
but the omission of any journal from the list would 
_ definitely warn the reader that no papers in that journal 
had been included, and thus leave him to look up that 
journal if he thought it likely to contain papers on the 
subject of his study. It would also save the reader 
who wished to make a more exhaustive study of any 
subject from referring to journals which had been 
already examined. This is the plan followed in the 
lists of journals at the end of each volume of the 
“Internationa] Catalogue of Scientific Literature.” 
In the present case, a list of the titles of the 400 journals 
examined would probably take up no more than three 
or four pages. 
The usefulness of these indexes depends entirely 
upon a wise choice of the headings under which the 
titles are grouped. It may be assumed that the Library 
Association is partly guided in its choice of headings 
by experience of the inquiries made by readers asking 
for books. 
The varicus headings are not arranged in any 
systematic way, and are not even divided according 
to the several sciences, but they follow one another 
in alphabetical order. The difficulty of this plan is 
that, when using such an index, it is not always possible 
to guess what heading will be chosen for a particular 
subject. This difficulty is, to a great extent, overcome 
in these subject indexes of the Library Association 
by the addition of numerous cross-references. Thus, 
under the heading “ Refrigeration” we find a cross- 
reference to “‘ Cooling Gases” indexed under “ C.” 
We might, however, not be so fortunate had we begun 
by looking up the subject of cooling gases under the 
_ heading “ Gas.” No doubt, the majority of those who 
use these indexes find a simple alphabetical arrange- 
ment of subjects more easy to understand than any 
systematic plan, and for that reason its use is justified. 
In the preparation of this Index special attention 
has been paid to applied science and technology. 
NO. 2781, VOL. 111] 
Among headings which have a large number of entries 
of titles of papers are aeronautics ; alloys; artillery ; 
automobiles ; coal; electric apparatus, power, heating 
and lighting ; ‘electroplating ; fish and fishing; gas 
and oil engines; glass; iron; metals; mines ; 
petroleum ; photography: ships and shipbuilding ; 
soils ; wireless signalling. 
(2) We are glad to find that the Library Association 
is continuing the publication of these subject indexes in 
other departments. Thus it has just issued a subject 
index for theology and philosophy (including folk- 
lore), indexing the literature of these subjects published 
in 1920, and occupying about ninety-six pages. This 
index contains titles of papers on psychology and 
psycho-analysis, as well as on philosophy and religion, 
and will therefore be of use to students of these subjects. 

Our Bookshelf. 
(1) Boiler Plant Testing: a Criticism of the Present 
Boiler Testing Codes and Suggestions for an Improved 
International Code. By D. Brownlie. Pp. xi+168. 
(London ; Chapman and Hall, Ltd., 1922.) ros. 6d. 
net. 
(2) Steam Power Plant Auxiliaries and Accessories. 
By Terrell Croft. Pp. xv+447. (New York and 
London: McGraw-Hill Book Co., Inc., 1922.) 153. 
net. 
(1) Mr. Brown.te has done great service in recent 
years in directing attention to uneconomical methods 
of steam production, and he has backed his criticisms 
by copious results of tests. The present volume 
contains an appeal for more rational methods of boiler 
testing, and criticises several existing codes, including 
that of the Institution of Civil Engineers. “A general 
impression also, on reading through the ‘ Civils’ ’ code, 
is that boiler plant testing is an extremely complicated 
and difficult operation, which involves a knowledge of 
chemistry and mathematics quite beyond the ordinary 
engineer, and can only be carried out by the Uni- 
versity graduate.” Mr. Brownlie shows that boiler 
testing must be regarded as a thoroughly practical 
proposition which is necessary for the strictly utili- 
tarian purpose of saving money. His criticism ‘is 
constructive in that he gives full directions for carrying 
out practical tests, and includes a typical set of report 
sheets, with figures showing the results. The book is 
a distinct contribution to the subject, and it is to be 
hoped will lead to an early discussion and revision of 
the present codes. 
(2) Considerable attention has been given recently 
to the formerly neglected auxiliary appliances con- 
nected with steam production, Pumps, feed-water 
heaters, fuel-economisers, condensers, steam pipes and 
traps are now taken seriously by the majority of 
engineers, and this consideration has led to the reduc- 
tion of wasted heat. The engineer will find a great 
deal of useful information in this volume, which is of 
the nature of a joint effort on the part of a number of 
concerns and individuals. The matter included is not 
only serviceable for the purposes of the design and 
