■416 H.H. Hou-orth—A Great Pod- Glacial Flood. 



glaciation is the Hessle Claj^ of the north-east, and the Upper Clay 

 pf the north-west ; the former being wholly of terrestrial, but the 

 latter at its lower elevations of submarine accumulation, and at its 

 higher of terrestrial. 



The interesting deposit described by Professor Prestwich in the 

 Quart. Journ. of the Geol. Soc. for May, 1882, as occupying hollows in 

 the Lower Chalk plain near Chilton, is, though derived from the higher 

 plain of Upper Chalk near by (and which, according to the Survey 

 ]\Iap, is covered with the " clay with flints "), I think so far posterior, 

 that it originated from the flooding of the land by excessive precipi- 

 tation as the minor glaciation passed away, which, in the concluding 

 part of my memoir " On the NeM'er Pliocene Period in England," 

 I have assigned as the cause of the thin bed of flattened fragments 

 of stone which, in South Lincolnshire, not only caps the loam with 

 angular fragments that originated in the process of annual thaw and 

 refreezing, but spreads also over gravel and sand not overlain by 

 that loam ; for though this Chilton accumulation contains, according 

 to Professor Prestwich, angular flint fragments abundantly, there 

 also enters into its composition much reconstructed chalk, as well 

 as a bed of laminated clay intercalated in a roughly stratified portion 

 of the deposit. 



Whatever may be the case with the Loess in China, it is clear 

 that the material here discussed by me has not originated from dust 

 clouds ; for the dust of a chalk country could hardly give rise to 

 a material in which, according to M. de Mercey, there is no appreci- 

 able quantity of lime, or the wind rupture the flints, and scatter 

 their fragments through the mass in the way described. And in 

 reference to the dust theory generally, one is tempted to ask why, 

 if dust gives rise, as is asserted, to a vast formation extending over 

 immense areas, and accumulating in places to the thickness of 1500 

 feet, in which are preserved the skeletons of the animals dying on 

 the land, those regions which have been land from a remote geo- 

 logical age do not present us with beds of this kind, containing the 

 remains of these animals which have lived during the long interval 

 between that age and the present, and thus perfect that Palseonto- 

 logical record which as yet is so imperfect ? 



VI. — Traces of a Great Post-Glacial Flood. 



3. The Evidence of the Valley Terraces. 



By H. H. HowoRTH, F.S.A. 



{^Continued from p. 311.) 



"^E must now turn to the theories which make these terraces to 

 be deposited by the rivers when so charged with water that the 

 whole valleys, from their solid foundations up to a height of at least 

 80 feet, were filled with water. These theories postulate no gigantic 

 denudations extending over limitless ages, but accept the valley 

 terraces as fluviatile deposits left along their own banks by the 

 rivers when, by means of exceptional causes, they were, at one 

 time, so flooded, that they actually reached the upper level terraces 



