JUNE 6, 1912] 
but the fact remains that the behaviour of cut and 
dressed stone in a town building is very different 
from that of the rock in its native habitat. 
Besides, occasions will continue to arise when 
some sort of test is required to confirm an archi- 
tect in his opinion and give him peace of mind; 
for none is so timid as an architect with a new 
and untried stone. 
Except for the purpose of discovering first 
principles, there is practically no need to test 
stones that have been long in use and are well 
known. The quality of the untried stone does 
require proving. To do this satisfactorily we 
need sound criteria founded upon knowledge of 
the properties of stones already used; and we 
should distinguish between those parts of a struc- 
ture subjected to the continued influence of mois- 
ture and those which are relatively dry. 
Prof. Hirschwald has been engaged for many 
years upon an examination of the weather-resist- 
ing properties of German stones, as exhibited in | 
old buildings, and by the application of great 
ingenuity and patience he has been able to trace 
the influence of the individual properties of the 
stone upon its durability. Upon this sound basis 
of experience he has formulated a very thorough- 
going scheme of stone-testing which, while it aims 
mainly at determining the degree of weather- 
proofness, at the same time embraces all the tests 
necessary for the estimation of mechanical 
strength. 
The method used by Prof. Hirschwald is to 
range a large number of stones obtained from 
buildings into about nine grades of quality, ac- 
cording to their present condition, the age of the 
structure being taken into account. He has then 
examined their petrological characters, porosity, 
degree of softening in water, resistance to frost, 
and their mechanical properties both before and 
after soaking and freezing. By correlating the 
observed results with the quality scale, and 
eliminating the effect first of one character and 
then of another, he is able to state numerically 
the value of any one of the structural and 
mineralogical peculiarities of the stone. 
As the result of this laborious preliminary work 
we have before us a means of estimating the 
probable weatherproofness of a stone within 
closer limits and with greater certainty than has 
hitherto been possible. 
Prof. Hirschwald’s earlier book, “Die Priifung 
der natiirlichen Bausteine auf ihre Wetter- 
bestandigkeit,” published in 1908, was out of 
print in the following year. The present work is 
practically a new and revised edition of the earlier 
one. Its division into two volumes of smaller 
size, of which vol. i. has appeared, is a. great 
NOweae23, VOL. 89]| 
NATURE 
| the Crustacea. 
345 
gain to the comfort of the reader. To save 
expense, some of the larger plates of the earlier 
single volume are discarded in favour of figures 
in the text without any disadvantage. The work 
has been improved by the addition of process 
blocks illustrating the apparatus actually em- 
ployed at the Charlottenburg laboratories, also by 
a fuller consideration of the tests for determining 
resistance to pressure, bending, shearing, and 
abrasion. As before, it is a storehouse of interest- 
ing numerical data concerning the properties of 
stone. 
OUR BOOKSHELF. 
A Guide to the Fossil Invertebrate Animals in the 
Department of Geology and Palaeontology in 
the British Museum (Natural History), Crom- 
well Road, London, S.W. Second edition. 
Pp. x+185+7 plates. (London: Printed by 
Order of the Trustees, 1911.) Price 1s. 
A. Bather’s guide 
It serves 
Tue second edition of Dr. F. 
will be even more useful than the first. 
| the student, who may never enter the British 
Museum galleries, as an introduction to inverte- 
brate paleontology, since the structure and habits 
of each class of animals are described, before 
the fossil remains are dealt with. The introduc- 
tions to Trilobita and Cephalopoda may be speci- 
ally mentioned. The interesting discovery of the 
dimorphism and double mode of reproduction of 
many foraminifera is stated on p. 24, with par- 
ticular reference to the Nummulites. Dibuno- 
phyllum is assigned ‘“‘stratigraphical importance ” 
on p. 54. A new drawing of the under surface 
of Eurypterus Fischeri appears on p. 87. We 
note that the class Arachnida, including the Mero- 
stomata, intervenes between the trilobites and 
The Crustacea receive more atten- 
| tion than is usually given to them; the interest 
of the beginner in paleontology often falls off 
| when he has mastered the structure of the trilo- 
| bites. 
| sion leads to inexactitude. 
Crabs and lobsters then appear to him 
altogether trivial; Dr. Bather, however (p. 100), 
attracts us happily to the primitive Dromiacea, 
and thence to the evolution of the crabs that are 
now familiar to us. 
The Brachiopoda follow the Arthropoda, and 
we finally pass to the Mollusca, the Cephalopoda 
being allowed thirty well-illustrated pages. The 
illustrations throughout are excellent, and cover 
fields of structure usually reserved for large and 
expensive textbooks. 
The language employed is so accurate that one 
does not at first realise how much matter has 
been compressed into a single sentence. The 
comparison between the structure of a_ starfish 
and that of a-sea-urchin (pp. 68 and 71) may 
be taken as an example. The term “flagellated 
chamber” on p. 29 seems a case where compres- 
On p. 74 we do not 
think that the author means to say that “some 
| urchins seem to have taken to moving generally 
