ae 
THURSDAY, SEPS 
CALCULATIONS FOR FLYING MACHINES. 
The Design of Aeroplanes. By Arthur W. Judge. 
Pp. viiit+212. (London: Whittaker and Co., 
1916.) Price gs. net. 
apes stability is not the only subject 
in which progress has been‘ retarded in the 
early stages of aviation. It is not so very long 
ago that Prof. Herbert Chatley read a paper on 
the calculation of the stresses in aeroplanes, and 
at the conclusion up jumped “Mr. I Don’t Agree 
With You” and said he “didn’t think” 
results would be of any value. The consequence 
of this system is that a person who is really an 
inventive genius has to spend the whole of his 
time in fighting against the opposition and pre- 
judice of people who “don’t think,” and he can 
produce original work only when he can get a 
post-graduate student or assistant to do the whole 
working of the necessary details. 
As a result of this retardaticn the literature 
dealing with the strength of the materials used in 
aeroplane construction and the stresses in their 
component parts is quite inadequate for the effi- 
cient development of aerial locomotion. 
So far as this book deals with details of experi- 
mental statistics, it fills a distinct want, and it is 
sure to receive favourable reviews in our engineer- 
ing journals. But a great deal of the subject- 
matter is nothing more or less than boiled-down 
mathematics, and the process of boiling down has 
in some instances been conducted in rather an 
amateurish way; moreover, the book contains 
statements that are certainly misleading, if not 
worse, for they cannot be correct if read as they 
stand. 
In the first place a large amount of space is 
taken up in the appendices with tables for the 
conversion of units and things of that kind, but 
no tables are given for use in logarithmic calcu- 
lations. Now it will be seen that almost all the 
formule quoted in the book, whether empirical 
or theoretical, involve products and powers rather 
than sums and differences, and for the efficient 
use of these formule a working knowledge of the 
use of logarithms is indispensable. The author 
may tell us that the class of mechanic for whom 
this book is written does not know how to use 
logarithms; if that be the case, the sooner he 
learns the better. He would then be spared an 
immense amount of time in turning over pages 
and pages of tables and possibly not finding what 
he wants at the end. The practice of mixing up 
tables of mere results of arithmetical operations 
with tables of experimental data cannot be too 
strongly deprecated. 
The treatment of such matters as moments of 
inertia is on the whole fairly satisfactory, but it 
‘would be better if the author had stated the 
theorem of parallel axes in words, besides giving 
the formula on p. 113. Experience in teaching 
elementary students shows that it is very difficult 
NO. 2447, VOL. 98] 
the | 
| to get them to interpret even the ee formula: 
| in a verbal Statement. 
The graphic method for constructing a curve 
the area of which represents the first or second 
moment of a given plane curve about a given axis 
is: very suitable for teaching purposes, though for 
actual working an alternative representation could 
be obtained more easily by the use of a cubical: 
parabola. 
In connection with the relative merits and de- 
merits of monoplanes and biplanes, statements are 
made on p. 31 which are on the face of them at 
variance with elementary considerations of common 
sense. We are told that a monoplane possesses a 
lower head resistance, due to the absence of separ- 
ate struts, ties, etc., and that it possesses relatively 
smaller moments of inertia about the axes of sym- 
metry. But it is surely obvious that the use of 
superposed planes renders it possible to reduce 
both the framework and the span with the same 
lifting area. If Mr. Judge’s statements are true 
of actual machines, it must be as the result of 
circumstances other than the difference between 
the one-decker and the two-decker type of wings, 
and this should be explained; otherwise the state- 
ments are calculated to mislead. 
There must, however, be something much more 
seriously in error in the statement of the “Bird 
Flight Data” quoted from Dr. Magnan’s con- 
clusions on p. 33. In the seventh line we are 
told that the total length of a bird in centimetres 
is equal to the cube root of the total weight in 
grams; in other words, that the relation 
between length and weight is the same as in a 
cube of water. Further, the area of the body is 
equal to the square of its length. In the next 
formula but one we are told that the weight of 
the wings in grams is 197 times the total 
loaded machine weight in grams. After this 
follow statements that the chord of the wing at 
the centre is 2°36 times, the length of the tail 
2°6 times, and the real length of the body 5°9 
times the cube root of the weight, which has 
already been stated as equalling the total length of 
the bird! 
While, therefore, the present book is to be 
welcomed as a step in the right direction, it will 
be seen that the subject still requires further revi- 
sion. Had it not been for the discouragement 
which Prof. Chatley’s early efforts received as the 
result of “discussions” consisting in expressions 
of premature opinions based upon _ insufficient 
data, we.do not doubt that by now Mr. Judge 
would have been handling the subject on more 
strictly scientific lines. 3 Ea; BE 
PALHOLITHIC MAN. 
Men of the Old Stone Age: Their Environment, 
Life, and Art. By Prof. H. F. Osborn. Second 
edition. _ Pp. xxvi+545. (London: G. Bell 
and Sons, Ltd., 1916.) Price 21s. net: 
ROGRESS in the study of prehistoric man has 
been so remarkable during the last few years 
that the demand for a rapid succession of more 
D 
