608 S. V. WOOD, JFN., ON THE NEWER 



have described, from the mudbank to the cutting-out method, in the 

 bottom of that valley. Here, in the Blackwater issue of the ice to the 

 sea, it lies at a height of about 100 feet *. It enters the valley of the 

 Chelmer, the next river south of the Blackwater, and there passes 

 undistinguishably into the lower part of the gravel, which extends 

 up the northern and eastern slopes of D anbury hill to the summit ; 

 for the Chalky Clay not having reached those sides of this hill, the 

 formation of gravel there went on uninterruptedly, so that V, c, and e 

 are continuous, as, but for the interposition of the Chalky Clay, they 

 would be on the western slope of the ridge in fig. VII. 



Along the northern slope of the Thames valley small patches of 

 gravel occur at various heights, representing that which, having 

 accumulated there while the Chalky Clay was forming, was mostly 

 washed away before it emerged. Of these one at Laindon Common 

 is traversed by the line of fig. VI. ; and they also occur above the 

 edge of the Chalky Clay in valleys tributary to that of the Thames, 

 Buch as that of the Eoding, in those places where having emerged, 

 and the ice not having reached so high or so far, this has not de- 

 stroyed them. None of these, however, pass over the Chalky Clay ; 

 but in the railway- cutting through the hill above Chipping Ongar, in 

 the fiord or channel represented by the Eoding valley, a considerable 

 bed of gravel was exposed, resting on the Chalky Clay that had been 

 deposited by the ice which ploughed out that channel. This is the 

 lowest point to which the clay desGends the side of the Thames 

 valley, or of any offset from it, such as that of the Eoding, and its 

 elevation is nearly level with the 175-feet mark on Ongar station. 

 This is in the Eoding issue to the sea. 



Mr. Prestwich, in vol. i. of the ' Geologist,' p. 241, describes the 

 Chalky Clay as both overlain and underlain by gravel in the railway- 

 cutting at Brickett Wood, near the centre of the north part of Sheet 

 7. The elevation of this cutting is about the same as Brickett- Wood 

 station, which is 256 feet. This is in the (Hertfordshire) Colne 

 issue to the sea. 



In the west centre of Sheet 46 I found the Chalky Clay overlain 

 by from 3 to 5 feet of red gravel on the hilltop at Southend 

 Stewkley in a clean section. This point is on the summit of the 

 water-parting that here divides the drainage-system of the Ouse 

 from that of the Thames, and its elevation is 482 feet ; but as it 

 forms a small island in Map 2 (PI. XXI.), occupying the centre of 

 the opening represented by those portions of this parting which are 

 below or but little above the line of the junction of c with d in their 

 vicinity, and the gravel was very coarse and flinty, I do not regard 

 it as a part of that which I am now describing, but as having been 

 derived from the melting of the ice that had mounted this island, 

 and lay high above the sea, and as similar to that of Norfolk de- 

 scribed in Stage IV. (<?'). The channels which here had, at the 

 stage of emergence shown in Map 2, connected the sea over the 



* Freshwater shells have been found in some of this gravel near Braxted ; but, 

 of course, as the sea retreated by the further rise of the land, the fresh water 

 followed it. 



