222 Rcvietcs — Nicholson’ s Life-History of the Earth. 
eartli, which are unequally divided by the centre of gravity, will be 
to cause the land to be antipodal to the water, and the slight ex- 
ceptions are near to the cii-cumference, dividing the globe into land 
and water hemispheres, which is where the exceptions would be 
expected. 
By these exceptions he concludes that the poles have moved in a 
curved direction. If we divide the earth by a plane (grand circle 
polaire) perpendicular to the equator and to the direction in which 
the position of the poles have been changing, the points of inter- 
section at the equator form two pivots for this motion, and here the 
effect of re-adjustment will be a minimum, while before and behind 
will be an area of elevation aud subtnergence respectively. If the 
motion is curved, the plane ( g.cp .) we have just supposed must cut 
the tangent of this curve at right angles. The changing position of 
this tangent changes the position of the plane, and the points of 
intersection are removed from the elevation to the submergence area 
on one side, and the opposite points from the submergence to the 
elevation area, so that land antipodal to land is the consequence. 
I. — The Ancient Life-History of the Earth. A Comprehensive 
Outline of the Principles and Leading Facts of Palasontological 
Science. By H. Alleyne Nicholson, M.D., D.Sc., M.A., etc., 
Professor of Nat. Hist, in tlie University of St. Andrews. 8vo., 
pp. xvi. and 407, and 276 woodcuts. (Edinburgh and London, 
W. Blackwood and Son.) 
T affords us much pleasure to bring under the notice of our 
readers a recent publication, which, we trust, will be the means, 
at any rate to a great extent, of assisting the Student of Palamntology 
in bis battle witli the many conflicting and unsolved problems of 
the Science. In bis “ Palaeontology ” Professor Alleyne Nicholson 
treated the subject from a purely zoological point of view, as a 
branch of the comprehensive Science of Biology. In the present 
work, on the contrary, the same subject is discussed as a sub- 
division of Geology, from its historical aspect, with the introduction 
of purely structural details, only so far as may be necessary to a due 
understanding of the ancient forms of our globe. Such a work as 
the present is best appreciated by those who have gone beyond the 
mere threshold of palfeontological Science, and learnt how difficult 
it is in working up any given subject to obtain an epitome of the 
various views which have been passed upon it. The comparative 
absence of works such as Professor Nicholson’s “Ancient Life- 
History ” from our language is a fact we must all deplore, but one 
we hope ere long to see remedied to a great extent ; and it is 
particularly on this account that the present work is the more 
welcome. True, we have Prof. Owen’s “ Palceontology,” a host in 
itself, the value of which was evinced by the fact that a second 
edition was called for before the book was a year old; but on 
EEVIEWS. 
