394 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May (), 



south side of the Colne, consists of thick beds of gravel and sand resting 

 upon London Clay. This gravel is for the most part well rolled, and 

 its stratification is very regular. Its upper and lower portions are 

 stony, while the middle consists principally of false-bedded strata of 

 sand. Fine sections are exposed by the drainage-works now going 

 on at the new cavalry-barracks at Colchester, and in pits in the 

 suburbs. The lowest bed, resting on the London Clay, is a coarse 

 gravel, well seen at Wivenhoe ballast-pit. 



I believe this extensive bed of gravel to be the old gravel which 

 elsewhere underlies the Boulder- clay. It crops out towards the 

 southern part of Essex, ranging from D anbury, where it attains 

 a considerable elevation, by Tiptree Heath to Colchester. It is seen 

 near the railway- station at Hadleigh in Suffolk, and in the same 

 county forms an extensive heath near Dunwich. 



There is an excavation in the lower portion of this gravel, in the 

 corner of Lexden Brick-pit, close to the kiln, where the following 

 section is exposed : — 



Section in the Brick-pit at Lexden. 



1 ft. in. 



1. Gravelly sand, about 16 



2 f Sand 20 



* \ Loamy sand with dark stains 6 



3. Coarse gravel with water, not pierced. 



The latter is doubtless the lowest member of the deposit, resting 

 upon the London Clay. 



The newer deposits of the Brick-field appear to rest upon a shelf of 

 the London Clay, and to abut against the old gravel above described. 

 The clay which, under the local name of " Strong Clay," is dug at the 

 north-west corner of the field seems to be the London Clay (a in 

 section, p. 395). There it has been excavated to the depth of about 

 12 feet; and at the lowest point ever reached pyrites are said to 

 have been found, and to have been pronounced by the late Mr. J. 

 Brown of Stanway to be " petrified wood," like that found at Walton- 

 on-the-Naze, where such remains are found in the London Clay. 

 There is a septarium to be seen in the river-bed just below. I have 

 not been so fortunate as to see this part of the pit in work. 



Upon this clay lies a bed of gravel (b), largely dug in those 

 parts of the field from which the superincumbent brick-earth has 

 been extracted. It is very different in character from the older 

 gravel above described, although its materials seem to have been for 

 the most part derived from the more ancient deposit. In the course 

 of its re-formation much of the sand has been removed, and a certain 

 proportion of clay incorporated instead, which renders the cementing 

 material more " binding." This gravel also contains a few large, 

 slightly rolled flints ; one which I saw must have weighed twenty- 

 five pounds. These flints were probably derived from the Boulder- 

 clay. The thickness of this gravel is about 7 feet ; but there are 

 other layers of clay and gravel, beneath the one which is worked, 

 which have not been proved. 



