will obtain only a partial view. The whole series 
will be equivalent to a single volume of. about 
120,000 words, but will compare unfavourably | 
with such a volume in unity and coherence. It is 
NATURE 
| 
unfortunate that there is so much freedom of | 
choice and so narrow a range of price in books for 
elementary schools; for unless we can have a 
| 
more definite practical aim in this and other types | 
of education we must expect variety of training | 
and outlook to give us a babel of tongues instead 
of a clear, resonant voice upon matters of national 
welfare. 
OUR BOOKSHELF, 
The Thermodynamic Properties of Ammonia. 
Computed for the use of Engineers from new 
experimental data derived from investigations 
made at the Massachusetts Institute of Techno- 
logy. By F. G. Keyes and R. B. Brownlee. 
Pp. v+73- (New York: John Wiley and Sons, 
Ine.; London: Chapman and Hall, Ltd., 1916.) 
Price 4s. 6d. net. 
Tus book contains the results of an experimental 
investigation carried out during the course of 
several years in the Research Laboratory of 
Physical Chemistry of the Massachusetts Insti- 
tute of Technology. The object of the re- 
search has been to determine the vapour- 
pressure curve and the specific heat-capacity 
of liquid ammonia and the isotherms of 
the substance, so that the already existing data 
might be critically examined and supplemented 
and the results obtained used as a basis for the 
computation of a new table of the thermodynamic 
properties of ammonia which would prove useful 
in controlling the performance of refrigerating 
machines. 
The first part of the book deals with the funda- 
mental thermodynamic relations and a discussion 
of the data and the computations. The various 
formule involving the relations between the 
entropy, Gibbs’s heat-function, the latent heat, 
the specific heats along the saturation line, the 
ordinary specific heats, etc., are obtained and 
tabulated for convenience. There are discussions 
on the methods employed to calculate the heat 
of vaporisation, the specific heat of liquid am- 
monia, and the entropy and specific heat of am- 
monia vapour. 
The second part of the book gives some forty 
pages of tables, in which the thermodynamic 
properties of the saturated and superheated 
vapour are given with the temperature as_ in- 
dependent variable in one set and the pressure 
in another. A Mollier diagram, in which heat- 
content is plotted against entropy, is added at 
the end of the volume. 
The book should prove of the greatest service 
in engineering practice, especially for those who 
have to deal with refrigerating machines. The 
tables are given in a very convenient form, and 
the explanatory matter at the beginning is 
-adequate and lucid. , Jade 
NO. 2448, vot. 98] 
69 
The Journal of the Institute of Metals. Vol. xv. 
Edited by G. Shaw Scott. Pp. . viii+392. 
(London :. Published by the Institute of Metals, 
1916.) Price 21s. net.- 
Tuts volume contains the papers presented at the 
annual meeting of the institute, with the discus- 
sion and correspondence to which they gave rise, 
together with abstracts of papers relating to the 
non-ferrous metals and the industries connected 
therewith. Among the papers is the Third Report 
to the Corrosion Committee, of which an account 
| was given in Nature on April 6. The paper by 
Mr. Withey on the analysis of aluminium and its 
alloys is a very good piece of work which will 
probably constitute the standard of reference for 
some years. The aluminium of to-day is liable to 
contain copper, iron, zinc, silicon, silica, nitrogen, 
and sodium. It contains notably more copper 
than the metal produced ten years ago, but in 
other respects is a purer metal. 
Prof. Stansfield’s paper on electric furnaces as 
applied to non-ferrous metallurgy contains much 
interesting and valuable information. Furnaces 
are classified under two main headings: (a) those 
in which metals are reduced from, their ores; (b) 
those in which metals are heated, melted, refined, 
and distilled. The former are electrolytic fur- 
naces, and are used for the production of metals 
by the electrolysis of their fused salts. Alumin- 
ium, sodium, potassium, magnesium, calcium, 
barium and strontium are produced largely, if not 
exclusively, in this manner; and other metals, 
such as zinc, are occasionally so obtained. The 
latter are electrothermic smelting furnaces, and 
are used for the production of metals from their 
ores with the aid of electrically generated heat. 
Occasionally the metal is present in the ore in the 
native state, but usually it is found as an oxide 
or other chemical compound, from which it must 
be liberated by a chemical reaction involving the 
use of carbon or some other reagent in addition 
to the necessary electrical heat. 
LETTERS TO THE EDITOR. 
[The Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous communications.] 
Science in Education. 
WE hear much of the place of science in education, 
but it seems sometimes as if its advocates would say : 
‘“When I mention science I mean experimental science, 
and not only experimental science, but industrial 
science, and not only industrial science, but paying 
science ’'"—to paraphrase Thwackum. 
Let us look at the French conception of science, as 
summarised in two fat volumes describing its progress 
in France, for the San Francisco Exhibition. In one 
volume are philosophy, sociology, education, mathe- 
matics, astronomy, physics, chemistry, mineralogy, 
geology, palzontology, biology, medicine, and geo- 
graphy. In an equal volume are Egyptology, classical 
