nERTFORDSnrRE NATTTRAL HISTORT SOCIETY, XXIX 



water to produce great results in a very short time. "With regard to Mr. Elsden's 

 remark as to the well-wooded appearance of our county being due to Ww jjost- 

 glacial deposits, he had seen beeches gro^ving almost on the bare chalk, and the 

 beeches of Hertfordshire were unsurpassed. 



Mr. J. Ilopkinson said that there was one point bearing upon Dr. Brett's 

 question as to the supposed increase in the thickness of the superficial soil wliich 

 might perhaps be overlooked, and that was that the surface of the earth, where 

 not perfectly horizontal, was constantly, thougli perhaps imperceptibly, on the 

 move. Frost and rain and other agencies disturbed the surface-soil, and the 

 tendency of every movement must, by the force of gravitation, be towards the 

 lower level. One result of this movement was that whenever a bank or wall ran 

 across sloping ground in any other direction than that of the slope, the ground 

 ■would be seen to be raised on the higher side above the general level, the bank 

 forming a barrier which interfered with the downward movement though it did 

 not entirely stop it. 



Mr. John Evans said that he would make a few observations on Mr. Elsden's 

 very interesting paper. One of the principal merits of the paper was this, that it 

 brought before them in a succinct form the opinions enunciated by various geolo- 

 gists — Professor Hughes, Mr. Penning, Mr. 8. V. Wood, and others — as to the 

 superficial deposits, not only of this county, but generally of the east of England. 

 Their discussion had run off on one or two points in connexion with some of 

 these, but he would just say a few words with regard to the more immediate 

 subject of the paper, the drifts of our county. Altliough he regarded the paper 

 as a very interesting contribution to our knowledge, he felt that in order to give a 

 thoroughly comprehensive account of all the drifts of this district an author must 

 be acquainted, not only with the eastern part of the county, but also with the 

 western. What might hold good concerning the neighbom-hood of Hertford and 

 that side of the county would not always hold good of the neighboiu-hood of 

 Watft)rd and this side of this county ; for on the eastern side of the coimty we 

 had all those marine glacial deposits of wliich the first part of the paper treated, 

 and on the western side, in this neighbourhood, although to some extent those 

 deposits may have existed at some time, at present the traces of them were im- 

 perfect, and" we had not the middle and lower glacial gravels in position. 



But in addition to this there was another important superficial deposit over the 

 greater part of the Chalk of this district, which though of the nature of drift, 

 was not, strictly speaking, a drift deposit by running water, salt or fresh. All 

 over certain districts of the chalk would be found a red clay, containing angular 

 flints, and they were e\'idently flints which had originally been in position in the 

 chalk, and from some reason or other the chalk had disappeared, leaving a red 

 clay. If we analysed the chalk, we should find a certain portion of clay 

 present. It was merely the insoluble part of the chalk -clay that was left in 

 position, the chalk having been dissolved out by the aid of carbonic acid filtering 

 into it. A great deal of the dissolution must have taken place in pre-glacial 

 times, for before the last glacial submergence this country was dry land, and this 

 deposit was being produced in the same manner as at the present day. 



There was still another class of deposits over a considerable portion of the 

 western portion of the county, — the London Clay and the beds below, which 

 extended very considerably further to the north-west than they now do. We 

 had proof of this in the small Tertiary outliers at Tyler's Hill and elsewhere, 

 showing that the London Clay beds which now terminated at Bushey must 

 originally have extended to Ashridge and nearly to Chesham ; for we had little 

 islands left from the denudation from the great Tertiary deposits of the London 

 Clay and the beds beneath. What we had left of the Tertiary beds was not 

 so much of the nature of di-ift as of slightly disturbed Tertiaries, and they were 

 deposited during the early part of the Tertiary period. Above the Tertiaries 

 we had the Lower Glacial beds, which had been deposited over an eroded 

 surface, showing that even before the glacial times there had been a considerable 

 denudation, which had taken place in some manner or other before the glacial 

 beds were deposited. Then we had the Middle Glacial deposits coming in, of 

 which we might find traces even in the western part of the county, for in the 

 gravels on the outer slopes of some of our dry valleys — Whippendale Bottom and 



