OcToBER 12, 1916] 
the standard Pentane lamp instead of the vague 
statement that “some other standardised source 
{than the standard candle], such as a Pentane 
lamp, is used,” without any indication of the way 
in which such standardisation is effected. We are 
glad to note, however, that Swan is given due 
credit for the prism-photometer, the origin of 
which is usually concealed so effectively under the 
name Lummer-Brodhun. 
In dealing with methods of measuring the co- 
efficient of linear expansion of a solid, the authors 
are scarcely fair to the optical lever, which is 
described as “‘not at all accurate” : we should say 
that much depends upon the experimenter! The 
attention of the student might also have been 
directed to the fact that all these methods give only 
the difference between the expansions of two 
bodies, one of which is supposed not to expand. 
On p. 336, in the experiment on expansion of 
air at constant pressure, mention should have 
been made of the error due to the saturated water 
vapour in the flask. The experiment given on 
P- 357 to illustrate Newton’s law of cooling 
will fail to do so unless the top of the calorimeter 
is closed; and the statement on p. 383 that “if 
the air is cooled down locally to this temperature 
[the dew-point] dew will be deposited on any flat 
surface exposed to this cooled air,” requires modi- 
fication. : 
In the section on magnetism we are sorry to 
see the statement (p. 393) that “a magnet of 
any shape usually behaves as though forces of 
attraction or repulsion originated from two definite 
points in its substance, which may be termed its 
poles.” Careful experiment soon convinces an 
intelligent student that a point pole is a fiction. 
Again, on p. 426, it would be well to point out 
that the tacit assumption that the moments of 
the two magnets are unaltered by their mutual 
action when in close proximity is not justified by 
experiment. 
In reference to the determination of the efficiency 
of an electric lamp, attention is rightly directed 
to the fact that this should be expressed as 
candle-power per watt, and not watts per candle- 
power. 
The book as a whole is a valuable addition to 
the list of text-books on practical physics, and the 
authors show an intimate acquaintance with the 
difficulties of both students and teachers which 
should make it very acceptable to both. 
Coa, S. 
ee i eee 
SYSTEMATIC ZOOLOGY. 
(1) The Fauna of British India, 
and Burma. Rhynchota: vol. vi. Homoptera: 
Appendix. By W. L. Distant. Pp. viii+ 248. 
(London: Taylor and Francis, 1916.) Price tos. 
(2) Catalogue of the Ungulate Mammals in the 
British Museum (Natural. History). Vol v. : 
Perissodactyla (Horses, Tapirs, Rhinoceroses), 
Hyracoidea (Hyraxes), Proboscidea (Elephants). 
By the late Richard Lydekker, Pp. xlv + 207. 
NO. 2450, VOL. 98] 
including Ceylon 
NATURE 
107 
(London: Printed by Order of the Trustees of 
the British Museum. Sold by Longmans and 
Co., 1916.) Price 7s. 6d. 
(1) M R. DISTANT’S Appendix to the account 
of the British Indian Homoptera in the 
admirable “ Fauna” has plenty to chronicle in the 
shape of novelties. In the Cicadas, so striking a 
group in the warm regions of the earth, he has to 
record as many as twenty-three new species since 
he dealt with the family in vol. iii. ; and naturally 
among those families which make less noise in the 
world the proportion of novelties is greater, even 
the little Jasside claiming thirty-two new forms, 
and the Cercopide, familiar to us in the person of 
the “cuckoo-spit ” insect, as many as fifty, a 
numbez more than trebled by the Fulgoride, most 
of which are not large and conspicuous like the 
celebrated “lantern-flies ” which popularly typify 
the family. The Membracide have more than 
sixty new forms described, which fully bear out 
the family reputation for eccentricity in thoracic 
appendages. Among the new forms described 
there is a large proportion of new genera, which 
are fully characterised, so that it is not surprising 
that the present volume is a fair-sized one; it is 
well illustrated, having 177 figures. 
(2) In addition to the Perissodactyles, Elephants, 
and Hyraxes, this concluding volume of the 
British Museum Ungulates contains an appendix 
to the Bovide, the general systematic index, and 
the index to the whole work. It has naturally 
suffered by the death of its author before he could 
revise, or indeed even complete, it; thus the lists 
of specimens in the museum do not go beyond the 
Horses and Tapirs, though in the remaining 
families the synonymy and localities are given. We 
are told that it has not been thought advisable to 
complete the volume on the full original plan, 
partly for lack of a competent author and partly 
for fear of detriment to science resulting from a 
mixed responsibility. It seems a great pity, how- 
ever, that descriptions were not added through- 
out, as the responsibility difficulty could surely 
have been got over by bracketing and initialling 
them; while it does not conduce to the credit of 
science to issue a work dealing with such impor- 
tant and generally interesting animals with its 
last volume disfigured and rendered half useless 
by their general absence. Some can be found in 
the accounts of the Hyraxes and of the Bovines 
in the Appendix; in the case of the one equine 
described, Equus quagga cuninghamei, the 
description is made misleading by the figure being 
incorrect, since it is said to have the mane well 
| developed, while the animal figured has scarcely 
any. This is one of the “ Burchell’s Zebra” sub- 
species, all of which, we think reasonably, are 
treated as forms of the Quagga, the typical race 
of which is extinct; but the Kiang, Chigetai, and 
Onager are given full specific rank. There are 
thirty-one illustrations in all, exclusive of an excel- 
lent portrait of Lydekker which forms the frontis- 
piece. mee 
