viii 
PREFACE. 
In regard to the general Palaeozoic Classification here put forward, I 
gladly avail myself of the opportunity to acknowledge how much I have 
been gratified by the perusal of the recent work, ' Geologie et Paleonto- 
logie,' of the Vicomte d'Archiac. In that truly philosophic history of the 
progress and actual state of our science, M. d'Archiac has clearly indicated 
the value of the step which was gained by reducing to method and order 
the former chaotic assemblages of rocks which passed under the names of 
4 grauwacke' and 1 transition' rocks — an effort, let me say, which could not 
have been successfully carried out and applied to great foreign regions 
had I not been so well aided by his associate in the French Institute, my 
valued friend de Verneuil. 
Lastly, after taking a general view of the history of the different races 
of animals which have succeeded to each other during all geological periods, 
I have, in the last Chapter, added a brief sketch of my long-cherished 
convictions respecting many of the former physical and mechanical changes 
of the earth's surface, as contrasted with any movements which have taken 
place in historical times. This, however, is a theoretical subject, on which 
differences of opinion necessarily exist. The view I take of such physical 
changes is, indeed, entirely apart from my main object, and may either be 
adopted or set aside without affecting in any way the truthfulness of the 
Succession of Eaces in Geological History as described in this volume. 
July 10, 1867. 
