250 ) 
[March, 
NOTICES OF BOOKS. 
Practical Physics ; Molecular Physics and Sound. By Frederick 
Guthrie, F.R.S., Professor of Physics in the Royal School 
of Mines. (London Science Class-Books Series.) London : 
Longmans and Co. 1878. 
Five-and-twenty years ago physical laboratories were almost 
unknown in this country. At the present time all our large edu- 
cational institutions possess a laboratory of this nature side by 
side with one devoted to chemistry. The fine physical labora- 
tories at Oxford, Cambridge, Glasgow, and South Kensington 
may be taken as examples of what such places should be like, 
and of how they should be worked. At the latter some dozens 
of students are successfully put through a course of practical 
physics every year, under the guidance of Prof. Guthrie, who 
has given us some of the results of his experience in the handy 
little volume before us. An admirable manipulator himself, he 
knows well how to instruct others ; and this work will not only 
be welcomed by the student, but also by the older man of science 
engaged in research, who will find many useful hints as to the 
preparation and use of apparatus. 
Starting with some definitions and experiments relating to the 
cohesion of solids, the author passes on to the cohesion of 
liquids and gases, introducing us to some of his beautiful expe- 
riments on bubbles and drops. We object, however, entirely to 
the term “cohesion of gases,” and we cannot at all understand 
the scope or object of the single paragraph (No. 19, p. 18) de- 
voted to the subject, which ends with the sentence — “ A more 
exact method is to place timed chronometers under bell jars 
containing various gases, and also in vacuo” The term 
“ volume-elasticity,” in the next Section, is awkward ; the piezo- 
meter, on the same page, could only be constructed and worked 
by a very skilful manipulator, and when in action would scarcely 
repay the infinite labour expended upon it. 
The subjects of Effusion, Diffusion, and Occlusion are ably 
discussed, and the most recent researches in each case are intro- 
duced. The short but comprehensive chapter on Specific Gra- 
vities abounds with practical hints, and details all the necessary 
processes. The ingenious way in which Prof. Guthrie has ap- 
plied singing flames to the demonstration of the refraction of 
sound by gaseous lenses (pp. 81, 82) is deserving of notice ; also 
the graphic representation (p. 102) of the cause of the clap, 
rattle, roll, and boom of thunder. The subject of Interference 
is ably and clearly treated. 
