Miscellaneous — Mr. Whitaker's Lecture. 143 



Jones. At the base there are unworn angular flints, with their surfaces coloured 

 green, lying on the lowest formation of the neighbourhood, the Upper Chalk, or 

 white chalk with flints, the top of which is in this section riddled with small tubular 

 hollows, that have been filled in with the green sand of the overlying bed. 



Attention was then drawn to the particular beds that should be searched for fossils, 

 namely, the basement-bed of the London Clay, the "leaf-bed," and the bottom-bed 

 of the Woolwich and Reading Series, and the chalk; and the speaker expressed a hope 

 that local observers would constantly visit the section, in order to preserve whatever 

 specimens might be found, and to record the bed from which each had been got. 



The geological conditions of the three formations shown in the pits were touched 

 on ; the lowest, the Chalk, giving evidence of having been deposited in a very deep 

 sea; the next above, the Woolwich and Reading Beds, being on the contrary of 

 shallow water origin, whether in the state of almost unfossiliferous mottled clays and 

 sands, as in this neighbourhood, or that of the fluviatile deposits that replace these 

 mottled clays to the westward (Kent) ; and the London Clay again pointing to a 

 deeper and a rather warmer sea, although the abundant plant remains that sometimes 

 occur in it show that land must have existed at no very great distance during its 

 deposition at such places. 



In the third place, the relation of the section to the general geological structure of 

 the district (which forms part of the "London Basin") was described, and by means 

 of sections (kindly brought by Professor Jones) the position of the Bagshot Beds, 

 which overlie the London Clay at no great distance, was shown, as also the uprise of 

 Upper Greensand from beneath the Chalk at Kingsclere. The other points noticed 

 were : {a) the uniformity of the Chalk over a large area ; {b) the varying nature of the 

 next series of beds ; (c) the uniformity of the London Clay, and its westerly thinning 

 away from 400 feet near London to less than 100 feet at Newbury, and to nearly 

 nothing in an outlier near Marlborough, where it is represented only by the layer of 

 pebbles at the bottom ; {d) the occurrence of beds of gravel, of late geological age, 

 over the various formations, firstly as cappings to many of the hills, and secondly 

 (newer) as deposits along the valleys, like those in which "flint implements" that 

 must have been made by the hand of man have been found elsewhere ; and (e) the 

 last geological formation of the neighbourhood, the peat and shell-marl of the Ken- 

 net. The formation of "pipes" or hollows in the chalk, by the dissolving away of 

 that rock by carbonated water, was also alluded to. 



Lastly, it was pointed out that the present surface of the ground was owing to 

 denudation, or the wearing away of the various beds, the present outcrops of which 

 were by no means their original boundaries, for they must once have spread far be- 

 yond where they are now to be seen. Evidence of this is given in the case of the 

 London Clay and the Reading Beds, by the occurrence of "outliers," or detached 

 masses, miles away from the main mass, with which they must once have been 

 connected. In the case of the Chalk, the former extension is shown by the occur- 

 rence of masses of flints, comparatively unworn, at great distances from the nearest 

 Chalk now left. The former continuity of the formations in the London Basin, with 

 the same formations in the analogous district known as th*e "Hampshire Basin," 

 was shown by means of the diagrums, as well as the disturbances that had thrown 

 the two areas into their present form and brought the various beds within reach of 

 the denuding forces. The agents of this denudation were firstly the sea, which had 

 planed down the beds to a more or less level surface, and secondly, the actions now 

 going on over the surface of the land by the means of atmospheric disintegration, or 

 weathering, of rain and of rivers ; actions which, from being for the most part of a 

 gradual character and every day before us, are liable to have their power much under- 

 rated, though when carefully investigated they are seen to be most powerful, and 

 able, in the course of long periods of time, to eifect very great changes. — From the 

 Neu-bury Weekly News, JMo. 297, October 10th, 1872. 



