286 PEOCEEDHiTGS OF THE GEOLOGICAL SOCIETY. [Feb. 26, 



near Cole-Green Station, and in some good sections on the hillside 

 south of the Mimram, near Tewin. 



Eoulder-elay sometimes, but rarely, occurs at the base of the 

 gravels of the Lower or Valley-Plain. There is a small patch of 

 reconstructed chalk and Boulder-clay resting on the chalk and 

 covered by the gravel, in a road-cutting south of Broad Oak End 

 Farm ; and obscure sections, proving the same order of superposition, 

 occur along the west side of the Beane, between that and Hertford. 



Near Ware, we have a very peculiar development of these beds. 

 Resting on the chalk (as seen south of Ware Park, and in the gravel- 

 pits near Ware, and as found by sinking in the brickfields west of 

 Ware), there is a varying thickness of sand and gravel, sometimes 

 with large boulders. This gravel rises in a long bank, running west 

 from Ware ; and behind the bank, and on its north slope, there is a 

 deep deposit of brick-earth, sometimes to 40 feet. This brick-earth is 

 an even-bedded loam, sometimes finely laminated, like the Warp of 

 the Humber, where the lamination is known to be due to tidal action. 

 Some of the beds of loam are folded and crumpled up, and then 

 covered by horizontal beds, in the manner generally ascribed to ice- 

 action. On the top there are irregular patches of Boulder-clay and 

 ferruginous subangular gravel : also near Hertford, in the brick- 

 field near the Infirmary, there is a brick-earth in the Lower-Plain 

 gravel ; and in the large gravel-pit on the north side of the same hill 

 there is a band of clay near the lower part, which seems to pass into 

 a brick-earth at its east end. On the whole, it would appear that 

 these brick- earths are local developments of the middle clays of the 

 Lower Plain. 



Some of these clays are very impervious to water ; and therefore 

 the gravel above them is stained red by the action of the surface- 

 water, while that below preserves its buff or grey colour ; but I have 

 not found any constant characteristic by which we can distinguish 

 the gravel above the clays from that below : in one section we find 

 the coarser deposit above ; in another it will be chiefly below. 



I would refer the gravels of the Lower or Yalley- Plain also to 

 marine action — from the Boulder-clay in them, from the great extent 

 of the middle clays, from the manner of occurrence of the banks of 

 gravel, and from the estuarine character of the Ware brick-earths. 



5. JRivei'- Gravels. — The deposits of the third period, or that of the 

 present rivers, do not call for any detailed remarks in connexion with 

 the points under consideration. They consist of the usual clays, 

 brick-earths, subangular and mixed gravels, and may be examined 

 along any of the rivers of the district, especially close to the railway- 

 station at Kingsmead, near Hertford, and near the mill east of Hat- 

 field Park. 



6. Summary. — Thus we have in the neighbourhood of Hertford 

 evidence of : — 



1st. A plain of marine denudation of great antiquity, on which 

 occurs a very marked pebble-gravel. 



2nd. A period of emergence, during which great valleys were 

 scooped out of that plain. 



