1875.] Notices of Books. 97 
11. It is postulated that, since the first appearance of life 
upon the earth’s surface, sufficient time has elapsed to 
have enabled such causes to produce all the specific 
heterogeneity now witnessed.” 
In a long chapter devoted to ‘* The Composition of Mind” 
the author arrives at the conclusion that the mind has grown in 
strength and complexity as the nervous system has grown in 
definiteness and coherence. Next he traces the evolution of 
mind, and in discussing this he clearly points out that the opera- 
tions of thought profoundly modify the structure of the brain, 
even in the course of a few years. The brain sometimes 
increases in structural complexity till the end of life, and often 
for many years after the age of 25. The brains of five very eminent 
men, examined by Wagner, were found to possess extraordinary 
complexities of structure,—ridgings, and furrowings, and deep 
irregular fissures. We are told, further, that the cerebrum and 
cerebellum are the organs in which ideal feelings and thoughts 
are generated, and that they are made up of tissues which 
undergo chemical changes with great rapidity. Exception is 
taken to Locke’s comparison of an infant’s mind to a blank 
sheet of paper, upon which experience writes knowledge: our 
author prefers to regard the infant’s mind as a sheet written over 
with invisible ink, which is made visible by the developer of 
experience. The remaining chapters of the second volume— 
on the Evolution of Society, the Conditions of Progress, the 
Intellectual and Moral Genesis of Man, Matter and Spirit, &c., 
—indicate a vast amount of reading, and a judicial examination 
of the more important now before the world. 
The whole work is intensely suggestive, both to the man of 
science and to the metaphysician. The author has worked up 
into a homogeneous whole the more prominent views of Herbert 
Spencer, Freeman, Buckle, Bain, and has added somewhat of 
his own. To those who wish to be au courant with advanced 
modern thought, from Darwinism to Sociology, from the me- 
chanical theory of heat to the nebular hypothesis, the book will 
be a great boon. Noman of science can read it without profit. 
The facts are grouped together in a clear logical manner, and 
although some of the definitions appear to us to be quite unne- 
cessarily complex, the book cannot be said to be overloaded by 
metaphysical technicalities. 
A Treatise on Magnetism, General and Terrestrial. By 
Humpurey Luioyp, D.D., D.C.L., Provost of Trinity College, 
Dublin, formerly Professor of Natural Philosophy in the 
University. London: Longmans, Green, and Co. 1874. 
THE author begins his treatise by giving an account of the 
general phenomena of magnetism, the processes of magnetisa- 
tion, and the measurement of magnetic force. He then passes 
VOL. V. (N. S.) fe) 
