114 



THE GEOLOGIST. 



more secure and perfect conditions. At the same time, the old rivers of 

 this Bagshot Sand Period traversed a land abounding probably in de- 

 composing granitic and syenitic rocks, such as we now find in Cornwall 

 and Brittany and also in the north-west of Spain, and bore down to 

 sea, during certain periods, the fine kaolin clays and other impalpable 

 soils of the district that now form the argillaceous beds and valuable 

 clays of the tertiary lands of Dorsetshire and Hampshire; whilst 

 stronger floods or currents drifted at intervals out into the same sea the 

 coarser sediment and fine quartzose grits forming the other portion of 

 the decomposing rocks before alluded to. I do not mean to say that the 

 changes were periodic, — they were more probably secular, resulting 

 from a change in the directions of the old rivers; for we cannot 

 suppose the great thick beds of sand and of clay to be each the 

 measure of a single period of flood or of calm. Each generally shows, 

 on the contrary, a change maintained for a given time, Mr. Kingsley 

 has called attention to a very interesting subject, requiring yet much 

 labour to elucidate. I throw out these remarks merely as a guide to 

 the direction in which I conceive they should tend ; the first step being, 

 not to go to a distance in search of a solution to a problem without first 

 looking, as Mr. Kingsley did, for an explanation on the spot, and within 

 the area, where the thing observed and questioned presents itself. 

 I am, Sir, 



Your most obedient servant, 



J. Prestwich, 



NOTES AND QUEEIES. 



The Rev. C, Kingslet's Lettek. (Page 75.) 



We are under the impression that Mr. Prestwich, in some of his papers on 

 Tertiary Geology, has referred the origin of the Dorsetshire clay beds and their 

 accompanying sands to the action of certain rivers that traversed an old granitic 

 and basaltic land, of which Brittany and Cornwall are remaining portions. 



What Mr. Kingsley terms " a guess" is a very good hypothesis that would find 

 much support in the published researches of Mr. Prestwich. The three lectures 

 delivered at the Clapham Athenaeum by the latter gentleman, and recently 

 printed under the title of "The Ground beneath Us," contain an outline map 

 of a portion of the old Tertiary lands, with much interesting information 

 bearing on the question. 



A very careful examination of the structure of the particular beds around Poole, 

 conducted almost yard by yard, would be essential to the full comprehension and 

 decision of the point Mr. Kingsley has mooted. 



A great deal of special information on the physical history of the Tertiary 

 sands and clays will be found in the numerous communications of late years, by 

 Mr. Prestwich, in the Quarterly Journal of the Geological Society ; and Mr. H. 

 Sorby's article in the Edinburgh New Philosophical Journal on the old sestuary 

 deposits of the Isle of Wight will also help in the research. 



Such valuable interrogations as Mr. Kingsley' s deserve every attention, and we 

 believe our readers may anticipate a ready reply, in our next number,'- from one 



• An exiilicit roply from Mr. Prestwich ha^1Ilg reached us just hefore going to press, vre have in- 

 •erteil it on the proccdiuj; page ; but as the above notice contains reference to published works on the 

 subject, we have thought it best to allow it to remain. 



