1825.]' of Alluvial a7id Diluvial Formations. 2i1l 



changing their inclination. Of such a state of things, the occa- 

 sional admixture of marine and freshwater deposits, and the 

 occasional alternation is the inevitable consequence.* 



Sect. 2. — Diluvial Formations. 



It remains for me briefly to notice the diluvial formations 

 which appear within the limits of the tract I have been describ- 

 ino-. They seem to have been rapidly and irregularly accumu- 

 lated by an inundation which acted with extrordinary violence j 

 for they are partly composed of broken masses of more ancient 

 strata, which are rounded and ground down by attrition, and 

 which in many instances have been transported from distant 

 parts of the country ; and they contain no alternations indicating 

 (as in the case of alluvial deposits) the long continued and tran- 

 quil operation of the agents by which they have been produced. 

 They rest on the ancient strata of the country without the inter- 

 vention of any other deposit whatsoever, and in instances with- 

 out number they form the basis of the whole alluvial detritus. 



The true relations of the diluvial detritus are beautifully 

 exemplified on the flanks of the chalk hills which skirt the 

 south-eastern side of the marsh lands above described. It is 

 constantly seen to rest immediately on the fundamental rock j 

 to follow all the irregularities of the surface ; to rise out from 

 beneath all the alluvial lands, and sometimes to lie in scattered 

 masses on the very top of the chalk downs. From thence it 

 may be traced, almost in a continuous mass, still further to the 

 south-east, where it is heaped up to an enormous thickness, and 

 overlies the newest tertiary beds which exist in that part of 

 England. From all these facts we are justified in concluding, 

 that the diluvial and alluvial deposits above described are not 

 only essentially different in their structure, but belong to two 

 distinct epochs ; the former class of deposits having been pro- 

 duced by some extraordinary disturbing forces prior to the exist- 

 ence of any portion of the other class. 



Were the order above given contradicted by the arrange- 

 ments of the superficial deposits in other parts of our island, we 

 should of course be prevented from drawing any general conclu- 

 sion from it. But I believe there is no inconsistency in the 

 order of our superficial deposits, and that the counterpart of the 



• A fine instance of tliis kind of alternation may be seen in the lower I'entowan 

 strenm-icork near )St. Austle. The ililuvinl tin ground (which is nearly thirty feet 

 below the level of hij^h-water) is covered with a deposit (about seven feet thick) of com- 

 pressed vegetable malter, leaves, roots, and trunks of trees, &c. all of which have evi. 

 dently been drifted intotlieir present position by floods, or perhaps by the sliile of a half- 

 formed turf bog. Over tliis deposit are a succession of marine beds (above twenty feet 

 thick) obviously accumulated, while the lower part of the v«lley was an estuary. 

 l/HKtly, a thick formation of peat, containing branches and trunks of trees, rises above 

 the level of hi'gh-water, and is surmounted by common vegetable soil. For a detnilcd 

 account of this section, »ee Gsol. Trans, vol. iv. p. 404, &c. 



