338 

tion of the style in which the subject matter is 
treated, about seventeen pages are devoted to a 
discussion of surface tension of a far more ele- 
mentary character than is usually presented to an 
average B.Sc pass candidate working in the 
laboratories of a British university, and on the 
other hand the thermodynamical formule which 
follow are written down without any consistent 
attempt at lucid explanation. Had the book been 
described under the last portion of the title alone 
it is not improbable that it might have proved of 
use to biological students who are weak in their 
knowledge of physics and chemistry, but even 
they would do well to remember that a little 
learning is a dangerous thing, and the danger 
is greatly increased when this small cargo of in- 
formation is allowed to sail disguised under the 
flag of a highly mathematical treatise. 
(2) In the matter of sailing under misleading 
colours, Col. De Villamil is another delinquent. He 
recently published an “‘A.B.C. of Hydrodynamics ” 
containing little or nothing on that subject which 
would be of use to a student pursuing a university 
course of study in hydrodynamics. By adopting a 
title closely resembling that of Lamb’s classical 
treatise, he thrusts on our attention a small book 
devoted almost exclusively to common or garden 
hydraulics, and dealing far less with the actual 
motions of the fluids than with the resistances 
which they exert on solids. Many of his state- 
ments are not very clearly expressed; for in- 
stance, what does he mean by saying that “in an 
incompressible liquid which has no free surface 
and whose envelope is inextensible all bodies 
moving in steady motion in it are stream-line”’? 
(p- 199), or, again, that “if any flat body of any 
shape be caused to move irrotationally round a 
fixed point, every point in the body will describe a 
figure which is an inverted reflexion of the body 
moving”? (p. 205). 
Had Col. De Villamil claimed to write about 
“ Practical Hydraulics,” it is probable that a good 
deal of the subject matter of the book would 
have been of use to engineers. In posing as a 
mathematical physicist the author is probably 
defeating his own ends. 
(3) Mr. Charles Darling’s lectures on “ Liquid 
Drops and Globules” present to an unscientific 
reader a simple and lucid exposition of a number 
of pretty experiments on liquids, many of which 
can be repeated by the most uninitiated at a 
trifling expense. The apparatus required is 
mostly of the simplest possible character, though 
for lecture purposes a lantern attachment is neces- 
sary. We note the author’s recommendation of 
tap-water as superior to “distilled water, which 
often possesses a surface so greasy as to retard 
NO. 2378, VOL. 95] 
NATURE 
| 

[May 27, 1915 

or even entirely prevent the desired result.” Curi- 
ously enough, the present reviewer’s experiences 
in spreading diatoms on cover glasses have con- 
firmed this difficulty of greasiness, and for mount- 
ing in resinous media the best results were fre- 
quently obtained by evaporating from a thick 
convex drop of ordinary filtered water heated to a 
high temperature, the impurities in the water 
being deposited round the edge of the cover, 
where they could be wiped off. The greasiness so 
often present in distilled water frequently caused 
the drop to tear away from the edges of the 
cover long before it had became reduced to a 
mere film, and often left actually more deposit on 
the diatoms than the less pure liquid. The 
same occurred when the drop was initially too 
thin. 
Readers who are unable to specialise in science, 
but who wish to interest themselves in some of its 
developments, can do no better than study a book 
of this kind. The experiments described form a 
delightful recreation for those engaged in duties 
of a non-scientific character, and at the same time 
they are directed on such lines as are likely to give 
them the closest insight into the intricacies and 
difficulties of scientific investigation. G. H. B. 
INSECTS AND. MAN. 
(1) Flies in Relation to Disease—Bloodsucking 
Hes, By Dr. Bs. blindles se Epyseweaoc: 
(Cambridge: At the University Press, 1914.) 
Price 12s. 6d. net. 
(2) Insects and Man. By C. A? Ealand. Pp. 343. 
(London: Grant Richards, Ltd., 1915.) Price 
12s. net. 
(1) HIS book is an attempt to combine in 
one volume the entomological informa- 
tion required by the doctor and the medical facts 
required by the entomologist, with regard to 
bloodsucking flies and the diseases they carry. 
The literature on this subject, being a special one, 
is very large, and is being added to daily. The 
whole subject is one that dates back only twenty 
years, and to attempt to present in a small com- 
pass a summary of these two aspects is no easy 
task. To do it successfully requires exceptional 
judgment in selecting what to omit and what to 
include, as well as a first-hand knowledge of both 
aspects of the subject. There is no evidence that 
the author has the latter, and the volume bears 
the impress of the laboratory, not of the tropics 
where these insects live and where men die daily 
from the diseases they carry. No one with actual 
tropical experience would omit from an account 
of measures taken against mosquitoes the use of 
traps and fumigants; no one with a first-hand 


