May 21, 1914| 
NATURE 20 
On 
asin Egypt. The author goes into details in other 
directions which it seems unnecessary to follow, 
and he estimates the area requiring irrigation and 
producing crops twice a year by a consideration 
of the colour changes. 
The Mechanical Engineer’s Reference Book. By 
H. H. Suplee. Fourth edition, revised and 
enlarged. Pp. xii+964. (London and Phila- 
delphia: J. 3B. Lippincott Company, n.d.) 
Pricé 26s. et. 
THE first edition of this well-known book was pub- 
lished in 1903. Sections are included giving 
mathematical formule and tables, information on 
mechanics, materials, machine design, heat, air, 
water, fuels, steam boilers and engines, internal 
combustion motors, and electric power. While 
much of the information supplied is good, and 
renders the book of service to engineers, there is 
a considerable amount of space taken up with 
matter which is surely unnecessary in an engineer- 
ing reference book. Some of the very elementary 
geometry given on p. 107 et seq. might be elimin- 
ated. There are few engineers who would require 
to consult a reference book in order to find out 
how to bisect a line by another line at right 
angles. The tables given on pp. 432 and 433 face 
one another, but the book has to be inverted before 
the second table can be read. On p. 274 there is 
a table giving the heights traversed by a falling 
body to seven significant figures. The American 
nomenclature in several places makes it somewhat 
difficult to obtain the precise meaning. 
The real test of the value of an engineering 
reference book is the up-to-dateness of its con- 
tents, otherwise the book will be used probably 
for the sake of the tables of areas and circum- 
ferences of circles, logarithms, etc. The presen‘ 
edition is by no means up-to-date in several ‘of its 
sections; those dealing with the strength and 
elasticity of materials and the properties of steam 
may be speciallv mentioned in this respect, where 
very little mention is made of the valuable develop- 
ments which have taken place during the last 
ten years. 
Outlines of Chordate Development. By Prof. 
W. E. Kellicott. Pp: v+471. (New York: 
H. Holt and Co., 1913.) Price 2.50 dollars. 
Pror. W. E. Ketuicotr’s introduction to the 
study of chordate development begins with Am- 
phioxus, which “affords in simple diagrammatic 
style, the essentials of early chordate ontogeny ”’ ; 
it lingers over the frog; it treats the chick more 
briefly, but lays emphasis on the embryonic mem- 
branes and the early stages; it ends up with the 
mammal, with particular reference to the early 
stages, the foetal membranes and the placenta, 
and the development of the external form. The 
book is well arranged, carefully and _ clearly 
written, and effectively illustrated. We _ think 
that it might have been made more interesting 
and distinctive by being more definitely correlated 
with phylogeny and comparative anatomy; but 
that, of course, is a big business. The well- 
selected bibliographies point the way. 
NO. VOL. 93] 
9 ~ 
2325; 
| placed in radium 
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. | 
Action of Radium Rays on Bakelite. 
A pisc 4-2 mm. thick of the light yellow variety of 
| transparent Bakelite was cut from a rod, polished and 
radiated with 8 and y rays from radium. The colour 
of the disc darkened to a wine-red after three days, 
and exhibited an absorption band A=5700—6000, 
which was not visible at first. The spectrum beyond 
A=4900 A.U. was also obliterated. A similar disc 
emanation became also rapidly 
coloured. The coloration extended to a depth of 
2 mm., and it could be completely removed by expo- 
sure to a temperature of 100° C. for about three hours. 
In order to see whether ozone played any part in 
_ the action a Bakelite disc was exposed to the gas for 
| work. 
six hours both alone and with radium near. Not the 
slightest coloration occurred. A portion of a rod was 
coated with paraffin wax and the radium rays caused 
to radiate the rod partly through the wax layer. There 
was no diminution in the rate of colouring under the 
wax. The effect, therefore, appears to be due to the 
direct action of B rays upon the Bakelite, for it would 
extend much deeper were it due to the y rays. This 
new substance may prove to be a useful filter for 
therapeutic use, especially as it is cleanly and easy to 
CHARLES E. S. Priuips. 
Physics Laboratory, Cancer Hospital, 
May 14. 
Respiratory Movements of Insects. 
THE concertina-like movement observable in the 
abdomen in the case of wasps and bees is, | believe, 
the visible evidence of the act of pumping the air in 
and out for respiratory purposes, and a similar pheno- 
menon may be seen in dragon-flies, except that in the 
| latter the movement is lateral and slow, whilst in 
wasps and bees it is axial and rather quick. I have 
not noticed any such movement in other groups of 
the Hymenoptera, and it is apparently absent in the 
Diptera, except Eristalis tenax, the common drone-fly, 
which obviously mimics the hive bee and other small 
species. If this movement really is due to respiration 
can any reader say why it is so comparatively re- 
stricted in the insect world? One would have expected 
soft-bodied insects, such as Diptera, to exhibit it more 
obviously than the more chitinous species amongst the 
Hymenoptera. I, and probably others, should be glad 
of any information throwing light on this matter. 
C. - NICHOLSON. 
Mr. NicHotson has hit upon an interesting inquiry, 
and will probably not be surprised to find that it has 
already received a good deal of attention. The re- 
spiratory movements of insects were experimentally 
investigated by the late Prof. Felix Plateau, of Ghent 
(‘Recherches Expérimentales sur les Mouvements 
Respiratoires des Insectes,”” Mém. Acad. Roy. de Bel- 
gique, tome xlv., 1884), who contributed a short sum- 
mary of his results to Miail and Denny’s ‘“‘ Cockroach ” 
(pp. 159-64). Respiratory movements can be demon- 
strated in dipterous flies, but in them the enlarged 
thorax is alternately contracted in different directions 
by the action of two sets of muscles, which are 
figured in Miall and Hammond’s “ Harlequin Fly,” 
(pp 1oo-ro2). Far more space than Nature could 
