580 
NATURE 
[Aucusr 8, 1912 
exception; for instance, a plane can be deformed 
while one line of it is fixed; again, most people 
would agree, after reflection, that a spherical cap 
is fixed when its circular rim is fixed; but our 
power of correct intuition is very limited, and the 
theorem can (apparently) only be proved by an 
analytical definition of deformation, and the theory 
of differential equations. 
Other chapters of the work, equally interesting, 
but more familiar, are those on curves in space, 
curves on surfaces other than geodesics, surfaces 
with plane or spherical lines of curvature (in- 
cluding Weingarten surfaces), triply orthogonal 
systems, and congruences of curves. The last of 
these is admittedly only a brief introduction, and 
the others, of course, can be supplemented from 
original papers. As to the latter, sufficient refer- 
ences are given to start the student on his re- 
searches; and most, if not all, of the leading 
names appear to have been included, though one 
cannot help missing Casey in connection with 
cyclides, and Kummer is not alluded to, though 
Hamilton is, when the author is discussing sys- 
tems of rays. 
It should be added that there are numerous sets 
of excellent examples, many of them based upon 
original papers. It is a pity that in the latter 
case references have not been given. Finally, the 
choice of symbols is very judicious, and a list of 
those which have special meanings is given on 
pp. xix-xxill. Dr. Forsyth may be congratulated 
on producing a work of great interest and value, 
which is perhaps the best treatise that he has ever 
composed. 
G) Bove 
OUR BOOKSHELF. 
Festschrift zum sechzigsten Geburtstage des Herrn 
Geheimen Hofrats Prof. Dr. Johann Wilhelm 
Spengel in Giessen. Herausgegeben von A. 
Brauer, L. Déderlein, L. Dollo, H. Ludwig, 
E. L. Mark, M. Weber, und A. Weismann. 
Erster Band. Pp. viii+6o09+ 32 plates. Price 
75 marks. Zweiter Band. Pp. vi.+863+41 
plates. Price 100 marks. Dritter Band. Pp. 
v+572+18 plates. Price 50 marks. (Jena: 
Gustav Fischer, 1912.) 
Tue Editor of the Zoologische Jahrbiicher has 
received a bulky tribute of esteem in the three- 
volume Festschrift that supplements this year’s 
issue of that journal. In the first volume the 
twenty-four essays are chiefly of systematic charac- 
ter. Even a list of these would occupy too much 
space, and we can merely draw attention to some 
of the more interesting points. A Pantopod-larva 
from Kiel leads Richters to suggest a crustacean 
origin for the group. Friese and v. Wagner con- 
tinue their admirable studies on bees by a con- 
NOM 2235) 89 | 
| eccurrence, distribution, and winning of oil. 
tribution to our knowledge of arctic-, alpine-, 
and steppe-forms of humble-bees. M. M. Metcalf 
describes an Opalina the nuclei of which fail to 
complete their mitosis. Many other papers of in- 
terest to systematists occur in this section. The 
second volume is chiefly anatomical, and the most 
important paper is probably that by Julin 
on the development of Pyrosoma. The other 
papers are largely descriptive and of interest 
mainly to the anatomist. The third section 
of the work is composed of general papers and of 
physiological ones. The most elaborate of these is 
the very detailed study of muscular contraction and 
movement in Lamellibranchs carried out by Poli- 
manti at Naples; but there is also a very careful 
study of the ciliary apparatus in the eyes of 
vertebrates by C. Hess, another on the spermato- 
phores of crustacea by E. A. Andrews, and an 
interesting account of the insect larvae which use 
their hind gut as an organ of propulsion. Upon 
the whole, however, it must be confessed that this 
Festschrift, in spite of its great bulk and beautiful 
plates, is a dull work. 
Oil-Finding: an Introduction to the Geological 
Study of Petroleum. By E. H. Cunningham 
Craig. With an Introduction by Sir Boverton 
Redwood, Bart. Pp. xi+195. (London: 
Edward Arnold, rg12.) Price 8s. 6d. net. 
Mr. CunninGHAM Craic has attempted to meet 
the demand, resulting from the widespread modern 
interest in petroleum, for a simple text-book of the 
art of oil finding, and has at least produced a 
book which is striking and interesting. The 
opening sentences at once arrest attention, for, 
unlike his predecessors who have regarded the 
origin of petroleum as an interesting academic 
question, having little bearing on its present dis- 
tribution or the search for productive areas, he 
starts off with the assertion that it absorbs and 
includes nearly every other question as to the 
His 
first care, therefore, is to deal with this question 
in no uncertain tones; for him petroleum is pro- 
duced by a metamorphosis from the accumulated 
débris of land vegetation, which has become buried 
by sediment and undergone a_ transformation 
analagous to, though differing from, that which 
has given rise to beds of coal; and the association 
of salt with petroleum, so constant that it has 
been regarded by most other writers as causal, 
becomes for him a mere accidental coincidence. 
Having dealt with the origin of petroleum, the 
author proceeds to describe the geological struc- 
tures which have been found most suitable for the 
accumulation of workable deposits, and concludes 
with a description of the methods of geological 
survey as it should be carried out in the examina- 
tion of oil fields which, though avow edly intended 
for beginners, contains several hints that are not 
infrequently overlooked by practised geologists. 
Though the book contains not a few assertions 
with which we cannot agree, it is both interesting 
and useful, when its avowed purpose is borne in 
mind. 
