a 
Fepruary 24, 1923] 
- 
NATURE 
249 

matter could have been made. The subject of photo- 
metry receives that attention to which its importance 
entitles it. On the other hand, radial motions are 
passed over with little mention. The confusion of 
Betelgeuse (p. 285) with a Bootis is curious, and other 
slips will be noticed. The spectroscopic determination 
~ of the parallax of a Centauri (p. 330) is due to W. H. 
Wright (not to Campbell). An argument occurring 
in the section on short-period variables is quite un- 
sound ; it would be just as reasonable to assert that 
the earth-moon system cannot be binary on similar 
grounds. But in such matters allowance ought to be 
made for the need for brevity. The subject of these 
three final chapters might easily be expanded into a 
large volume. 
It cannot be denied that the book is marred by a 
number of minor errors. They may be attributed to 
_ the want of the author’s revision, owing to the recent 
g 
eclipse expedition of which he was in charge. In 
passing a book through the press the most zealous and 
competent editor can scarcely replace the author 
himself. Certain corrections are called for in the 
interest of accuracy and for the instruction of the 
serious student, and will be easily introduced in a 
later edition. In the meantime, the general reader 
should find in the present work an interesting review 
of the methods and principal features of modern 
astronomy, from which he can gain an insight into its 
spirit and general trend. ER Cir. 
A Text-book of Metallography. 
An Introduction to the Study of Metallography and 
Macrography. By Dr. L. Guillet and A. Portevin. 
Translated by L. Taverner. With an Introduction 
by Prof. H. C. H. Carpenter. Pp. xvi+ 289 + Plates 
exvii. (London: G. Bell and Sons, Ltd., 1922.) 
30s. net. 
HE handsome volume before us is the largest 
general text-book of metallography that has 
yet appeared in English, and the preface states that 
the authors have in preparation a still larger treatise, 
which is evidently intended to deal with the subject 
very fully. Their presentation is essentially French, 
and is worthy of the school founded by Osmond and 
Le Chatelier. In any historical account of the origins 
of metallography the name of Sorby is necessarily 
mentioned, but neither the authors nor Prof. Carpenter, 
who writes an introduction, quite do justice to his 
remarkable work. Sorby not only.devised the method of 
preparing and examining micro-sections of metals, but 
he also described correctly and identified the principal 
constituents of several varieties of iron and steel, and 
recorded their structures in photographs which leave 
NO. 2782, VOL. 111] 
nothing to be desired in clearness and accuracy. These 
photographs appeared in 1887, or seven years before 
the classical paper of Osmond, in which the study was 
advanced many stages further. Sorby’s experiments 
were actually made, at least with the lower powers, 
in 1864, but the lack of interest taken in them by 
manufacturers led him to put them aside until the 
work of Martens again directed attention to the use 
of the microscope in the study of metals. 
The characteristic feature of this volume by Messrs. 
Guillet and Portevin is its wealth of illustrations, 
mostly excellent. The least satisfactory are those 
showing the process of recrystallisation in cold-worked 
metals, for which better material is now available. 
Taken as a whole, however, the plates reach a very 
high standard. The equilibrium diagram and other 
theoretical sections are treated briefly but clearly, and 
more stress is laid on practical applications than is 
usual in text-books. The physical properties of alloys 
are only cursorily reviewed, and the experimental 
determination of changes of volume might well have 
been described, in view of the fact that dilatometric 
results are used freely in the account of the special 
steels. The chapter on mechanical testing describes 
French machines, and needs to be supplemented for 
English readers. No fatigue test is included, and the 
list of etching reagents (awkwardly called ‘“ etchants ”’) 
is rather meagre, and might well be enlarged. The 
concrete studies of groups of technical alloys are very 
useful, and bring together a large amount of information, 
but the section on alloy steels is out-of-date ; it is 
based on the older papers of Guillet, and the important 
group of light alloys receives little attention. 
The most novel feature of the work is the section 
devoted to macrography. This is actually older in 
date than microscopical metallography, having been 
employed by Widmanstatten in 1808 in the study of 
meteorites. It is not so well known as it should be 
that Sorby employed “ nature-printing” to record 
the structure of converted bars in 1864, printing from 
an etched surface by means of printers’ ink. This 
method was extensively used in this country during 
the war for examining shell and other forgings. The 
authors do not describe nature-printing, but give a 
good account of the etching of metallic surfaces for 
macro-photography, and of the interpretation of the 
results so obtained. This section is of great value. 
The translation is clear and smooth. Proper names 
have suffered rather badly (Bénédick for Benedicks, 
Marten for Martens, Brani for Bruni, Carnilley for 
Carnelley, etc.) but other misprints do not appear to 
be numerous. As a comprehensive survey of a subject 
of growing importance, the book is likely to have a 
wide popularity. CH. D; 
ria 
