Ixiv PKocEEDrisres, 



4. " Climatological Observations taken in Hertfordshire in the 

 year 1896." By John Hopkinson, F.L.S., P.G.S., F.R.Met. Soc, 

 Assoc. Inst. C.E. [Transactmis, Vol. IX, p. 241.) 



Field Meeting, 3ed April, 1897. 

 CHESHAM AND TYLER'S HILL. 



The first Field Meeting of the season was held in very un- 

 favourable weather, the day being bitterly cold, rain threatening 

 and a little falling, and the roads and paths being muddy from the 

 heavy rains of the previous month. The meeting was organized by 

 the Geologists' Association of London and was under the direction 

 of Mr. Upfield Green, F.G.S., the Hertfordshire Society being 

 invited to join in it, but no member took advantage of this invita- 

 tion who was not also a member of the Geologists' Association. 



Leaving Chesham Station at about 3 o'clock, a somewhat steep 

 hill was ascended and the fields were crossed to the brickfields on 

 Tyler's Hill, also known as Cowcroft. This is a wooded hill of 

 which the upper part consists of an outlier of the Lower Eocene 

 beds capped by a thin bed of Drift. The outlier is one of a series 

 which range in a line nearly parallel with the north-western 

 boundary of the main mass of the Tertiary strata of which they 

 at one time formed a part, the intervening portion having been 

 removed by denudation. The presence of these outliers is probably 

 due to a slight change of dip of the Chalk on which they rest 

 causing the beds to lie in a trough and so affording them protection 

 from denudation. That they now form the highest ground is due 

 to subaerial denudation having less effect upon such beds of clay 

 and sand than upon the chalk by which they are surrounded, which 

 probably undergoes more waste from chemical dissolution than from 

 mechanical attrition. The wood on Tyler's Hill, the presence of 

 which is due to the nature of the subsoil formed by the outlier, also 

 affords a great protection from denudation, most of the rain which 

 falls upon it being absorbed by the trees so that it does not wash 

 away the soil. 



Several sections in the brickfields were examined. In one about 

 25 feet of the Heading Eeds are exposed, the upper portion 

 consisting of about ten feet of white sand with a thin bed of clay 

 on the top, and the lower of about twelve feet of greyish sands 

 and laminated clay reposing on a layer of green-coated unwater- 

 worn flints and of pebbles which rests on a nearly level surface 

 of the Upper Chalk. In another section the surface of the Chalk 

 was seen to be very irregular, in fact worn away so as to form 

 pinnacles between which is clay with unworn flints, pebbles, and 

 broken shells, and with brick-earth on the top. And in a third 

 section about fifteen feet of the Reading Beds are surmounted by 

 about twelve feet of the Basement Bed of the London Clay, the 

 Bending Beds consisting of buff sands passing upwards into mottled 

 red and white sands, and the Basement Bed of laminated sandy 



