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POPULAR SCIENCE REVIEW. 
are some of the subjects selected by the biographer ; but the second volume 
in reality takes in the history of the railway system with all its fights before 
Parliament and with the public, together with a graphic description of the 
difficulties which had to be overcome when crossing rivers, or making levels 
to suit the prejudices of people, or to contend with natural causes. There 
are excellent portraits of George and Eobert, and engravings of the Britannia, 
the Conway, and the High-level bridge at Newcastle, and of the Victoria 
bridge at Montreal. The book is in the highest degree interesting, and well 
worthy of careful study by all who have faith in steady industry and enthusiasm. 
PKINCIPLES OF BIOLOGY.* 
T O readers of modem philosophy Mr. Spencer is tolerably well known as 
a clever writer and a deep thinker. Anything, therefore, which claims 
his authorship has a fair chance of securing a favourable reception at the 
hands of scientific reviewers. The book which has now been issued by his 
publishers has been “ coming out ” in numbers for some considerable period, 
and constitutes only the first volume of a work which, if carried on upon 
the scheme already laid down, must eventually assume very formidable 
dimensions. Employing the temi biology in its most comprehensive and 
accurate sense, to embrace all those phenomena relating to the subtle com- 
bination of forces to which we apply the term life, the author’s aim has been 
to associate the various laws and theoretical inductions framed concerning 
the latter. Such has been his first object ; but his second one has been to 
demonstrate, from a careful analysis of those laws, and from an effort to 
show their marked correlation, that life, in its varied and numberless forms, 
is but the result of a grand process of evolution. In working out this 
problem, Mr. Spencer is but following in the footsteps of the more dis- 
tinguished modern men of science, and of course his labour has been in great 
part confined to collating evidence. The latter he has done in a manner 
highly creditable to himself ; and although in some few instances we observe 
statements which appear to us hardly supportable, still the writer is not to 
be held responsible for them. We wish, too, that in his next volume he 
would lay aside the style so common among writers upon metaphysics, and 
adopt a language more in keeping with the plain truths of science than that 
employed by him in some instances. Apart from the conclusions at which he 
arrives (and we shall not gainsay them), the book is, from the nature of the 
subjects which the author is obliged to introduce, full of interesting 
matter, whiph must prove highly attractive to the educated or even the 
ordinarily intelligent reader. We object to all definitions of life in the pre- 
sent state of science ; for inasmuch as we are yet unable to explain the pro- 
cesses of life in their entirety, a definition can be at best but a short expres- 
sion of what we see going on within an organism. But we feel particularly 
opposed to accept the writer’s definition, that Life is the definite combination 
of heterogeneous changes, both simultaneous and successive.^^ It seems to us 
* “ The Principles of Biology.” By Herbert Spencer. Yol. I. London: 
Williams & Norgate. 1864. 
