IN PART OF NORTH-WESTERN ESSEX. 2[T 



with the line of railway. The area is bounded to the north-east by 

 the Blackwater as for as Shalford, and a line drawn from that point 

 through Stebbing Mount to Dunniow High Wood completes the 

 northern limit of the area of observation. 



(Ireat changes have occurred at Braintree since I'rof. Prestwich 

 visited the spot and drew his sections, presumably in 1849. Those 

 sections are now all concealed. New sections have, however, been 

 opened at higher, at the same, and at lower elevations, and these are 

 in the main confirmatory of those he drew. It is to be regretted 

 that the section in Black Notley cutting (of which he has given 

 such an instructive illustration, Plate vii.. Fig. 6) is now covered by 

 talus, and there is no present equivalent in that neighbourhood ; that 

 is to say, no section at Braintree now shows the \V'estleton Beds 

 overlaid by the Middle Glacial Gravel. They are generally sharply 

 overlaid by Boulder Clay. 



The section shown by the Black Notley cutting I have used as a 

 standard of comparison with other beds. These gravels and sand 

 vary greatly in their composition, but not to such an extent as to be 

 mistaken for the Glacial deposits of the district. Moreover, the 

 variations have proved valuable in cases where the section was small 

 and only one particular variety of sand or shingle was exposed. The 

 sand is sometimes ferruginous, sometimes of a rich yellow colour, 

 and in this case contains almost always abundant, though minute, 

 scales of mica. Sometimes it is quite white, like silver sand. It is 

 generally finely comminuted, and, with the pebbly gravel, contains but 

 little clay. The gravel is well described in Prof. Prestwich's paper 

 {I.e. p. 133). (jenerally it is made up about half of Quartz pebbles 

 and half of Flint, both ivell rounded. It has but very few sub-angular 

 flints, and none sharply angular ; and only a small proportion of the 

 stones in number are larger than a pullet's egg. Moreover, the 

 pebbles are enclosed in a matrix of yellow or iron-coloured sand, 

 which has but a small admixture of clay. In this respect the gravel 

 differs radically from the Middle Glacial Gravels of the district. 



The Middle Glacial Gravels are well developed at Felstead and 

 Great Waltham, and generally just south of the area under con- 

 sideration ; and, however much these gravels may vary in more 

 widely separate localities, they certainly do not, for the few miles in or 

 near the tract under consideration, show a great amount of variation. 

 Gases occur where, as Prof. Prestwich points out, they are hopelessly 

 mi.xed up with the Westleton series ; but sufficient instances remain 



