Feb. 15, 1883] 
NATURE 361 
and bya range of hills, the Koh-Amir, from the Sistan 
Hamun. A ride performed under great difficulties across 
the Kharan desert to the neighbourhood of the Sistan 
swamp placed all these points beyond doubt, so that the 
drainage system of the hitherto almost unknown region 
along the Perso-Baluch frontier, from the Lower Helmand 
to the Arabian Sea, has now been satisfactorily deter- 
mined. From Sistdn the travellers made their way by two 
new and parallel routes right across North Baluchistan to 
Jacobabad in Sind. The numerous typographical points 
recorded both here and throughout West Makrdan are 
embodied in the accompanying map, which is on a large 
scale, and which forms an important contribution to our 
knowledge of the south-eastern section of the Iranian 
plateau. Inthe appendix are given the directions, dis- 
tances, and other useful details of no less than twenty-two 
routes in the same region. The relief of the land and its 
salient physical features are also further illustrated by 
numerous sketches made on the spot by General Mac- 
gregor. Much valuable matter regarding the Baluchi 
and Brahui tribes, and the present political situation of 
Baluchistan, is scattered over the pages of this pleasantly 
written volume. A. H. KEANE 
PHYSICAL OPTICS 
Physical Optics. By R. T. Glazebrook, M.A., F.R.S. 
(London: Longmans, 1883.) 
HIS is the most recent volume of the well-known 
series of Text-books of Science published by Messrs. 
Longman. Mr. Glazebrook is already favourably known 
as an accurate experimenter and an able theorist in the 
subject of which this volume treats, and it is therefore 
unnecessary to say that the treatise under notice contains 
a large amount of authentic and interesting information 
on all branches of the subject. We must confess, how- 
ever, to a certain feeling of disappointment after going 
through the book, arising chiefly from the fact that the 
author does not appear clearly to have made up his mind 
as to the class of readers to whom the book is to be 
useful. Those who have had any experience in real per- 
sonal teaching of the artisans and students in science 
schools for whom the volumes of this series are stated to 
be intended, will soon perceive that Mr. Glazebrook has 
assumed an amount of mathematical knowledge and 
ability which very few of them possess. On the other 
hand results are occasionally assumed, the investigation of 
which would be quite within the reach of those university 
students who will probably form the larger part of the 
readers of the treatise. For instance, the investigation 
of the focal lines of a pencil refracted in a principal plane 
through a prism, and the condition of their coincidence 
in the position of minimum deviation, is settled by an 
“it may be shown,” although the analysis required is 
certainly not more difficult than much that is given in the 
book, and the point to be elucidated is of considerable 
importance. 
The author has intentionally introduced a large quantity 
of matter which is usually considered to belong to the 
kindred subject of Geometrical Optics, and although there 
will probably be a difference of opinion as to the advantage 
of this proceeding, there will be none as to the clearness 
of the explanations and the excellence of the diagrams 
employed. There does not seem to be quite so much 
“matter new to the text-books”’ as is hinted at in the 
preface, but on the whole the book furnishes a good 
account of the subject, comparable with Lloyd’s well- 
known treatise on the Wave Theory of Light, and dealing 
with many points which have been investigated since the 
date of the latter work. 
Where there is so much of good, it is a pity that it 
should not be made better, and there are a few points in 
which perfection has not been reached. In places there 
is a tendency to a slipshod and “high-falutin” method of 
expression which may be forgiven in University Extension 
lectures delivered extempore to popular audiences, but 
which is hardly suitable for a scientific treatise. On p. 2 
we have a graphic representation of the author raising his 
arm and of the effect thereby produced on his own body. 
Later on in the book, quitting the solitary first person, he 
becomes more friendly to his readers, and speaks of “ our 
apertures, our lens, our prism, our eye,” and so on. He 
even presently hands the apparatus entirely over to the 
reader and directs him to perform the operations for 
himself. A more serious matter is the want of care in 
revising the proofs. For instance, on p. 202 an effect is 
spoken of as “ that due to a single aperture multiplied by 
a number of apertures,” which is nonsense, the author’s 
meaning being ‘‘ multiplied by #ze number of the aper- 
tures.’’ Again, on p. 141, the sentence—‘‘ They are dis- 
tinct from the coloured rings of thick plates discovered 
by Newton, and were described by him as follows,” gives 
an almost opposite meaning to that which the author 
intended. It ought to read ‘‘ which were described.” 
The proper names are not treated with the accuracy 
and uniformity which are desirable. We have Fraunhofer 
usually, but on p. 316 Frauonhofer. Huygens appears on 
p- 15, but more frequently the name is met with as 
Huyghens, while the possessive case assumes the dif- 
ferent forms of Huygben’s, Huyghens’, and on p. 226 
Huyghens’s. Defects of this kind mar the pleasure with 
which the book would otherwise be read, and seem to: 
indicate that more care might have been advantageously 
bestowed on the original composition as well as on the 
revision of the proofs. Possibly the author wishes to 
leave something to be looked for in the second edition, 
for the speedy arrival of which he has our best wishes. 
OUR BOOK SHELF 
The Year-Book of Pharmacy, 1882.  8vo. 
(London : Churchill, 1883.) 
THIS volume contains a number of exceedingly inte- 
resting papers and extracts. The most interesting 
are those which relate to the artificial production of 
organic alkaloids, for when we obtain such a knowledge 
of the constitution of these bodies as will enable us to 
make them artificially, we may hope that a new era wilh 
commence in medicine, and that the results of the treat- 
ment of disease will be more definite and satisfactory 
than heretofore. 
Prof, Ladenburg, who has been engaged for some time 
on researches into those alkaloids which dilate the pupil, 
is still continuing his researches, and has obtained very 
interesting results indeed. Atropia when heated with 
strong hydrochloric acid splits up into a base, tropine, 
and an acid, tropic acid. While pursuing his investiga- 
tions upon tropine, the author came to the conclusion 
that this base contained an alcoholic hydroxyl group 
Pp. 607. 
