\ 



DRIFT IN THE VALLEY OF THE CAM, ESSEX. 335 



Glacial Drift. Instead, however, of the usual comparatively thin 

 sand or gravel being found, the boring-tool, after passing to a depth 

 of 340 feet, chiefly through loamy beds, did not succeed in reaching 

 the Chalk, and the -work was abandoned. The Drift, therefore, 

 must here go down to a depth of about 140 feet below the level of 

 the sea ; how much deeper we know not. 



As on the other, or eastern, side of the main stream, the Chalk 

 crops up at a distance of about 1000 feet, or a trifle more, and 

 only a little below the 200-feet contour, we have here, allowing a 

 difference of level of 15 feet between the two sites, an easterly rise 

 of the underground Chalk-surface of at least 325 in 1000, on the 

 presumption that the Chalk would be touched at once on deepening 

 the bore, and that the Drift occurs right up to the eastern edge of 

 the marsh. We may fairly, therefore, call this a slope of about 1 in 

 3, over a long distance, and it may, of course, be steeper. 



Wenden. 



Hitherto we have been dealing with tracts where the great sheet 

 of the Drift spreads down to the bottom of the valley, though at 

 last on the western side only. Prom Wenden northward, however, 

 this sheet of Drift is cut through by the valley, the flanks of which 

 are then chiefly of Chalk. 



It is at and near this place that the abrupt way in which the 

 Drift lies against the Chalk has been seen, in open sections, as 

 figured by Mr. Penning ; and turning again to the evidence from 

 deep borings, we have here two sections showing a great depth of 

 Drift. 



One of these, at Mr. Collins', north-eastward of Audley End 

 Station, and, measuring on the six-inch Ordnance Map, about 

 550 feet eastward of the "Neville Arms," reached the Chalk at the 

 depth of 220 feet. The other, which is somewhat nearer to the 

 outcrop of the Chalk, was made for some cottages belonging to Lord 

 Br ay broke, and is on the southern side of the road, a little north 

 of the " Neville Arms," and about 650 feet W.N.W. from the former 

 well. In this case the Chalk was not reached until the boring had 

 been made to the depth of 290 feet. 



As, by a measurement made by Mr. Ingold, the Chalk occurs at 

 only 3 feet below tlie ground (the 3 feet probably being soil) 

 at the railway, only 140 yards N.N.AV. of the second boring, it 

 follows that, between these two places, there must be a fall of the 

 Chalk-surface of 293 feet. Presuming that they arc at about the 

 same level (the site of the boring is probably a trifle the lower), this 

 is a slope of 1 in 1*43. 



Mr. Collins' well, though at a slightly lower level, seems to show 

 the beginning of the easterly rise of the Chalk, which rock is bare 

 at the lower part of the slope on the other, or eastern, side of the 

 valley, the Drift coming on again higher up, at about the 200-feet 



Q.J.G.S. No. 182. 2 a 



