THE JURASSIC DEPOSITS WHICH UNDERLIE LONDON. 731 
been preserved in the office of the Richmond Waterworks by Mr. 
Peirce, the resident engineer, and these enable me to identify the 
limits of the several strata overlying the Chalk without difficulty. 
The locality in which the well was commenced is in the oldest 
part of the town of Richmond, and materials which had evidently 
been disturbed were met with down to the depth of 10 ft. Of the 
very sandy gravel which covers all that part of the Thames Valley 
around Richmond and Kew, only a slight remnant, about 10 in. 
in thickness, was found undisturbed. 
The London Clay, presenting its usual characters, was then met 
with, and the sinking was continued for 160 ft. in this formation. 
The Lower London Tertiaries were represented by 44 ft. of the 
well-known variegated Plastic Clays of the Woolwich and Reading 
series, underlain by 124 ft. of sand and sandstone, the base of the 
series being formed by clays with a lignite-band and the usual layer 
of rounded flint-pebbles. The strata below this pebble-bed evidently 
belong to the Thanet Sand, which in its characters precisely agrees 
with what is seen of the formation at many points along its outcrop. 
The upper portion of the series at Richmond consists of light ash- 
coloured sands having a thickness of 133 ft.; while the lower 
portion, with a thickness of 8 ft., consists of darker-coloured greenish 
sands with a considerable admixture of argillaceous matter and 
many glauconite grains. 
At the bottom of the Thanet Sand was found the band of unworn 
flints, coated with a dark green substance, which is everywhere so 
characteristic of the junction of the Tertiary strata with the Chalk. 
The whole thickness of the Thanet Sand, including the band of fiints 
at its base, is 224 ft. 
The complete section down to the Chalk is as follows :— 
itis) bas 
Miadesoroun dn ce joencecasisee saa eben caaeceaet LOMO 
Post-Tertiary sandy gravel ......... Pee he isniesine 10 
ondony Clay: VAG meets ects mene cceacn ee anes 160 O 
(Mottled G@edtandtereem) claysis2.----- sees 44 0 
ly Nellow- samdig)x. Wee" yet hae factsheet oO) 
Woolwich an j iHandysandstome mocha s..ctesc.css. tase eee 4 0 
Reading Series. Inioht-colauned Clays eeccss. aocee eee scree ee ae 0 
| Clay with much lignite and a band of well- 
Oe roundedipebblesratmts bases ssc. sss eee: ree LG 
Tightjash-orey sail yea... sescnes seeedesclios steelers 13 6 
Thanet Dark-coloured argillaceous sand with much 
Sand. SlantCOnibe® Coleen capone eee e sess eae 8 O 
iBandok green-cOabed! Hints) nasscesee acess eeceee 1 O 
White chalk with flints. 
IV. Tue CHAyx. 
The Chalk was struck in the Richmond well at a depth of 253 
ft. from the surface, or about 236 ft. below Ordnance datum line 
or mean level of the sea. In two other wells at Richmond, one at 
the old Waterworks and the other at the Star-and-Garter Hotel, the 
top of the Chalk appears to have been met with at about the same 
level. 
