558 



NATURE 



\Oct, 19, 1876 



Fig. 2.- 



-Purbe;;k and Portland Beds at Tilly Whim, near Swanage ; the former being the 

 light-coloured strata above, the latter the darker strata below. 



Fig. 3. — Section at Writtle, near Chelmsford.- 2. Chalky Boulder Clay (Upper Glacial). 

 I. Sand and Gravel (Middle Glacial). 



Fig. 4. — Peprhyn Slate Quarry. 



author may possibly have been actuated 

 by the conviction that unless the pendu- 

 lum of opinion, which has so long been 

 firmly held at one end of the arc by 

 official influences, were allowed to re- 

 bound to the extreme limit in the opposite 

 direction, there would be little chance of 

 its finally attaining a position of stable 

 equilibrium between them. Looked at 

 from any other point of view, we must 

 confess that we cannot regard the attempt 

 here made totally to revolutionise the 

 classification in question with much satis- 

 faction. We had hoped that the day had 

 long since gone by when the divisions 

 between geological periods were to be 

 regarded as governed by anything more 

 than convention, or as serving any other 

 purpose than that of convenience of re- 

 ference. Breaks, whether stratigraphical 

 or palaeontological, in the series of forma- 

 tions, are purely local phc^ieinena j and it 

 is certain that if stratigraphical geology 

 had taken its rise only so far away as in 

 Eastern instead of in Western Europe, 

 the divisions of the great systems, and 

 even of those larger periods (which Mr. 

 Woodward calls " cycles ") would have 

 been wholly difierent to that which has 

 been actually adopted. But although the 

 classification of the geological periods is 

 a purely artificial one, yet it has its uses, 

 and nothing but confusion can result 

 from attempts to unsettle its landmarks 

 without sufficient cause. Such being the 

 case, we are surely entitled to ask what 

 useful purpose can possibly be served by 

 including, as our author does by his own 

 showing, considerably more than one-third 

 of the whole thickness of British sedi- 

 mentary deposits under the name of Cam- 

 brian 1 Is not a Cambrian system, en- 

 larged beyond all reasonable proportions, 

 equally objectionable with an overgrown 

 Silurian ? This question has passed be- 

 yond the stage when it can be regarded 

 simply as a battle-ground for the partisans 

 of rival reputations. Now that Sedgwick 

 and Murchison have both passed away, 

 let us rather seek to be guided by the 

 principles which determined the action of 

 the greatest of their contemporaries in 

 respect to this controversy ; gladly avail- 

 ing ourselves of that which is good and 

 true in the splendid work of both the 

 observers, let us build it into our geolo- 

 gical system, there to stand as the noblest 

 monument of their genius ; and for their 

 mistakes, let these pass into the oblivion 

 which awaits the memory of the injustice 

 and animosity which were unworthj of 

 either of them. 



There are one or two other points which 

 we would venture to suggest for the 

 author's consideration in the event of his 

 being called upon, as we hope he will be, 

 to prepare a second edition of this work. 

 As the different formations or groups of 

 strata belonging to the same system which 

 occur in different parts of the country are 

 treated of consecutively, although in many 

 cases they were doubtless formed con- 

 temporaneously, it would be well to keep 

 the latter fact as prominently before the 



Jl 



