Notices of Books. 
413 
1876.] 
tinuous process of cooling, but it may have every now and then 
fired up afresh, and the time taken to reduce it to a certain tem- 
perature may have been much longer than if it had gone on 
always steadily losing heat.” We may add that this view agrees 
not badly with certain well-known astronomical phenomena. 
Nor should the very untrustworthy nature of mathematical 
speculation, where not constantly controlled by an appeal to 
actual facts, be left out of view. If mathematicians were till 
lately in error to the extent of i-30th part in such a comparatively 
simple matter as the distance of the earth from the sun, what 
weight can we seriously attach to Sir W. Thomson’s speculation 
as to the past direction of the solar system ? 
In the dispute between the Uniformitarians and the Catastro- 
phists, Mr. Green takes an intermediate position. He holds it 
highly probable that “ when the earth was hotter than it is now 
all the phenomena which depend directly or indirectly on the 
internal heat, such as metamorphism, volcanic energy, and 
contortion, must have been proportionally more energetic; and 
if the sun was at the same time hotter, all the geological opera- 
tions depending on meteorological conditions, such as denuda- 
tion, must have gone on faster and on a larger scale than now.” 
Still he holds that, for the period over which our researches 
extend, Uniformitarianism may be practically correct. 
As regards the climatic changes which the earth has under- 
gone, such as the glacial epochs and the genial Miocene period, 
our author inclines to the views expounded by Mr. J. Croll, in 
his “ Climate and Time in their Geological Relations : a Theory 
of the Secular Changes of the Earth’s Climate.” 
We shall look forward with interest to the appearance of the 
second part of the work before us, and we think we may safely 
congratulate the Yorkshire College of Science on including in its 
professorial staff so able an expounder of a fascinating and im- 
portant science. 
An Introduction to Animal Morphology and Systematic Zoology. 
By Alexander Macalister, M.B., Professor of Comparative 
Anatomy and Zoology, University of Dublin. Part I. : In- 
vertebrata. London : Longmans, Green, and Co. 
The author of this work states in his Preface : — “ In teaching 
zoology and comparative anatomy I have found that students 
desire to have a text-book in their hands to enable them to learn 
the terminology of the science, and by giving them a connected 
view of the varieties of animal forms to assist them in remem- 
bering the practical instructions of the class-room.” 
This want he has endeavoured to meet, and, in our opinion, 
with good success. Of course minute details must not be looked 
