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 
claj's 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 QUERIES. 
Tub Rev. C. Kingslet's Letter. (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 Clapliam 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 aestuary 
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 CTplicit reply from Mr. Prestwich Imving reached us just before going to press, we have in- 
serted it on the preceding page ; but as the above notice contains reference to published wo. ks on the 
suliject, we have thought it best to allow it to remain. 
