592 MR. 0. A. SHRUBSOLE ON THE 



indications are that a considerable amount of valley-erosion must 

 have taken place before the implements now found at 235 feet above 

 sea-level were placed there. A still greater amount of erosion had 

 taken place before the implements and mammalian remains now 

 found at 197 feet above sea-level reached their present position. 



With regard to any indications that are afforded as to former 

 climatic conditions, it is not until we reach the level last mentioned, 

 in descending order, that any very marked irregularities in the 

 deposit of gravels occur ; the higher-level valley-deposits, like the 

 plateau-gravels and the hill-gravels, presenting no marked difference 

 from the results of ordinary water-action. Irregular bedding is 

 again observable as belonging to the considerably later epoch when 

 the valley had been lowered to about 150 feet above sea-level. 



The very large percentage of quartzites and other rocks not occur- 

 ring in situ in the Thames-valley in the composition of the gravel 

 at Norcot (page 589), 294 feet above sea-level, may be taken as an 

 indication that glacial action and submergence had taken place at no 

 distant interval from the time when it was laid down. 



So far, then, as the gravels of the valley can be considered repre- 

 sentative of important stages in its history, the indications are of a 

 severe climate occurring at an early stage and recurring later 

 on. Traces of Man occur in many of the stages intermediate be- 

 tween the Norcot gravel and that of the comparatively low-level at 

 Elm Park and Kennet Mouth. Traces of other mammalia are found 

 at those last-mentioned localities, but not of Man. 



A comparison of the types of the implements found at the different 

 levels shows that, assuming the highest level to be the oldest, the 

 pointed type, with a thickened butt, might be adjudged to be the 

 most ancient in the district. On the other hand, the Ightham im- 

 plements, found at heights of from 380 to 500 feet above sea-level, 

 described by Prof. Prestwich*, and considered by him to be " pos- 

 sibly pre-giacialt", do not differ in any special manner from those 

 found in this district at levels lower than that of Caversham. 



This similarity was alluded to by Dr. Evans t ; and, as there 

 is reason for supposing the Ightham implements to have formed 

 part of gravels which have been in a great measure removed by 

 denudation, it is probable also that many of the implements found 

 in the lower levels at Reading have been derived from gravels which 

 have been swept away. This is the more likely when we have regard 

 to the mixed character of the types generally found in the lower 

 levels, and to the fact that a river can accumulate a considerable 

 thickness of gravel in a short time. It is not likely, therefore, that 

 the implements of various types found at any particular place repre- 

 sent the gradual entombment of the specimens in a slowly accumu- 

 lating deposit spread over a considerable interval, but rather the result 

 of amixing-up of materials derived from gravels of various dates and 

 from various levels. 



The position in which the implements occur in these lower-level 

 gravels is also worthy of notice. Wherever the gravel attains any 



* Quart. Journ. Geol. Soc. vol. xlv. 1889, pp. 270-296. 

 I- Ibid. p. 292. J Ibid. p. 295. 



