620 
written for students having an elementary 
knowledge of the subject. 
The plan of the book includes a statement of 
the problem, its financial aspect, its mechanics, 
the scientific side and the practical side as well. 
The scope of the problem, choice of site, char- 
acter of installation, type of engine and boiler, 
and their design, construction, erection and 
operation, are excellently stated, including the 
finance of the case. Finance is taken as the 
controlling factor, and the costs of steam-power 
are indicated and illustrated. Rankine’s method 
of apportioning the engine to its work, as a 
financial proposition, is described, its fatal de- 
fect shown, and the later and corrected system 
of use of true ‘ curves of efficiency ’ is described. 
In designing, the method of Professor Barr of 
ascertaining the results of general experience in 
determining the factor of safety is described 
and its results given. 
A brief and well-arranged statement of the 
fundamental principles of thermodynamics is 
presented and an excellent outline of the scien- 
tific side of the problem is laid down. The 
great defect of the real engine, its internal 
waste of heat and steam, is well described, as 
are the results of later investigations to deter- 
mine its amount and its laws of variation. 
R. H. THuRsTon, 
Catalogue of the Fossil Bryozoa in the Department 
of Geology, British Museum (Natural His- 
tory). By J. W. Grecory. The Cretaceous 
Bryozoa, Volume I. London, Longmans & 
Co. 8vo. Pp. 457. 17 pl. 
The long list of British Museum (Natural 
History) catalogues has received another wel- 
come addition in the Catalogue of the Creta- 
ceous Bryozoa, Volume I., by Dr. J. W. Gregory. 
This catalogue is devoted entirely to descrip- 
tions and figures of the Cretaceous bryozoa, the 
groundwork, terminology, classification, ete., 
having been laid by the author in an earlier 
work of the same series: The Catalogue of the 
Jurassic Bryozoa in the British Museum (Nat- 
ural History), published in 1896. In a second 
volume, to appear later, the author hopes to 
give a general introduction to the} Cretaceous 
bryozoa, a list of localities with their horizons, 
and a bibliography. The catalogue is intended 
SCIENCE. 
[N. 8S. Vou. XIII. No. 329, 
to be complete, to include every recorded spe- 
cies, though the large number of inadequate 
descriptions by early writers and their unrec- 
ognizable figures will leave much in doubt. It 
is a question whether science would not be a 
gainer if much of this early work could be au- 
thoritatively set aside. The desire to conform 
too strictly to the law of priority or to do jus- 
tice to early workers sometimes results in even 
greater injustice to later workers. 
’ The present volume treats only of the Cyclo- 
stomata. This division Dr. Gregory raises to 
ordinal value and divides into the suborders : 
Tubulata, with the families Diastoporide, Id- 
moniide, Entalophoride, Hleide; Cancellata, 
with families Horneridx, Petaloporide; Dac- 
tylethrata, with families Clauside, Terebel- 
lariidz, Reticuliporide. 
The large size of the present volume is itself 
evidence of the fine collection which the British 
Museum has accumulated. The author notes 
the large additions recently made to the collec- 
tion and laments that an American collection 
was received too late to be included in this 
volume. Doubtless the second volume will 
supply the deficiency. No work of importance 
has been done on hryozoa from gecondary and 
tertiary formations of America since the work 
of Gabb and Horn in 1860-62. The interesting 
bryozoan fauna of the Cretaceous marls of New 
Jersey has begun, however, to attract the atten- 
tion of workers in this country as well as abroad. 
The greatest of the many merits of the vol- 
ume under consideration is the great care taken 
in collecting full synonymy and in giving care- 
ful, accurate descriptions with measurements. 
The rather complicated mode of relative meas- 
urements which the author employed in the 
volume on the Jurassic bryozoa he has aban- 
doned for the simpler and more easily compre- 
hended plan of absolute measurements. We 
believe the author adopts the correct position 
when he says that dimensions, while important, 
seem to him of far less value than is attached 
to them by some continental writers, who make 
them the chief specific distinctions. It is no 
doubt true that, in some groups, each species 
is very constant in its dimensions, while in 
other groups species are very variable in this 
respect. But the same is true of other charac- 
