﻿222 Reviews — Nicholson's Life-Histori/ of the Earth. 



earth, wliich are unequally divider! by the centre of gravity, vp^ill be 

 to cause the land to be antipodal to the water, and the slight ex- 

 ceptions are near to the circumference, 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 and submergence respectively. If the 

 motion is curved, the plane (g.ep.) 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^ZBVIEAATS. 



I. — The Ancient Life-History of the Earth. A Comprehensive 

 Outline of the Principles and Leading Facts of Palaeontological 

 Science. By H. Alleyne Nicholson, M.D., D.Sc, M.A., etc., 

 Professor of Nat. Hist, in the University of St. Andi'ews. 8vo., 

 pp. xvi. and 407, and 276 woodcuts. (Edinburgh and London, 

 W. Blackwood and Son.) 



IT 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 Palseontology 

 in his battle with the many conflicting and unsolved problems of 

 the science. In his " 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 appi^eciated by those who have gone beyond the 

 mere threshold of palaeontological 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 



