VI 



Yarmoutli. But by the gradual encroachment of the sea its 

 drainage area has been greatly reduced, and at last its valley has 

 actually been reached and cut across by the waves, so that the 

 streani there enters the sea, and the lower part of the valley is left 

 almost dry. 



One of the following chapters has been devoted to a description 

 of the nature and position of the various anticlinal and synclinal 

 folds which play so large a part in the geological structure, not 

 only of the Isle of Wight but of the whole of the south-eastern 

 mainland. From the evidence obtainable in the Island we know 

 that these plications of the rocks were produced at some time 

 subsequent to the deposition of the Oligocene strata. Elsewhere 

 we obtain proofs that they were completed before the Pliocene 

 period. The limits of their geological date are thus fixed. 



The Appendices include a number of well-sections and borino's 

 collected and arranged by Mr. Reid. The fossil lists formerly- 

 dispersed through the Memoir have been thrown together into 

 one tabular statement which has been prepared by Messrs. Reid 

 and Strahan with the assistance of Mr. G. Sharman and Mr. E. T. 

 Newton, Palaeontologists of the Geological Survey. A geological* 

 bibliography, compiled by Mr. Bristow, has been cadded to the 

 Memoir. 



ARCH. GEIKIE, 



Director- General. 

 Geological Survey Office, 

 London, 

 April 1889. 



[Since this preface was written, and while these pages are 

 passing through the press, Mr. Bristow has been removed from us 

 by death. We hoped that he would huxe lived to see the final 

 publication of this Memoir, in the preparation of which he took so 

 keen an interest. The correction of his " Notice " formed his last 

 piece of scientific work, and in returning it to me only a few 

 weeks before the illness from which he never recovered, he 

 expressed with characteristic courtesy his approval of all that had 

 been done to make this new edition a fitting termination to the 

 labours of his long career in the Geological Survey. W^e cherish 

 his memory as a loyal and helpful friend and a distinguit^hed 

 colleague. 



A. G. 



June 24th, 1889.] 



