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as the term is, the chill taken off ; or, to use other words, the water requires 
to he made a few degrees warmer. The reason for this is, that when water 
of too cold a temperature is used, it abstracts the heat so suddenly from the 
surface of the steel, that it causes a too sudden contraction of the surface 
steel, and the expansion of the interior steel in its red-hot state is more than 
the hardened crust can bear ; consequently it frequently causes the steel to 
break. 
u It is quite probable that the interior steel for the moment becomes both 
heated and expanded in a higher degree by the sudden compression, for the 
sudden contraction of the surface steel by the sudden loss of heat must act 
on the interior steel something similar to a blow from a heavy hammer on 
the pressure of a squeezer ; and if the steel should happen to be a little too 
hot at the time of dipping it into pure cold water, there is as much danger 
of its breaking as there is of a glass bottle breaking when boiling water is 
poured into it : heat and cold act on glass and other brittle substances in a 
similar manner that they act on steel. When boiling water is poured into 
a glass bottle, the expansion of the inside glass is so sudden that it is more 
than the outside can bear ; consequently the bottle breaks. If glass is heated 
to a red heat and plunged into cold water, it breaks into a quantity of small 
pieces from the sudden contraction ; if a stone is thrown into the fire, it 
breaks from the sudden expansion of its surface.” 
BRITISH SPONGES.* 
I N one of our last numbers we noticed the first volume of Dr. Bowerbank’s 
Monograph, and we spoke of it as a work which every naturalist in- 
terested in the study of the Protozoa ought to become acquainted with. 
But there were other features in the first volume which gave it a special 
importance over the part now issued : it dealt very fully with the general 
anatomy and physiology of the Amorphozoa. In volume ii. we find merely 
a continuation of the description of genera and species ; this, which was 
begun in the first part, though of little interest to the physiologist or the 
general zoologist, is to those who are engaged in the pursuit and identifica- 
tion of species simply indispensable. The descriptions complete the account 
of the British Sponges, and are more comprehensive and detailed than those 
of any other systematic treatise we are familiar with. The author, in the 
first instance, gives a classified list of all the species described in the volume, 
ranging them, according to their affinities, in orders and suborders. In 
giving an account of the species, he first supplies the characters in true 
technical fashion ; as, for example, in the case of Grantia compressa, he begins 
thus, u Compressed, foliaform, slightly pedicelled, surface even, armed with 
flecto-claval spicula.” Then he pursues the happier and — for the general 
reader — more satisfactory method of giving a long general description of 
the sponge, in which all the striking points in its external anatomy are 
given in familiar language. The present volume contains no plates, but 
the 'descriptions are lucid and comprehensive. In the first volume, Dr. 
Bowerbank gave a tabular view of the systematic arrangement of sponges, 
* u A Monograph of the British Spongiidse.” By J. S. Bowerbank, 
LL.D. F.R.S. &c. Vol. H. London : Published for the Ray Society by 
Robert Hardwicke, 1866. 
