243 
TIIK GEOLOGIST. 
gravels of the London district, is seldom to be determined ; the cutting 
itself throws no light on this subject, or, at least, nothing very definite. 
But a ballast pit has recently been opened at the Watford end of the 
Bricket "Wood cutting, and immediately south of the line, which exposes 
a section of much interest. The Boulder Clay has there almost thinned 
out, leaving but a seam one to two feet thick, whilst both above and 
below it is a thick bed of gravel. The lower sandy gravel, which con- 
sists chiefly of sub-angular flints and flint pebbles, with some quartz, 
sandstone, and old-rock pebbles, with subordinate scams of whitish sand, 
has a clean, washed appearance. The upper gravel consists of very simi- 
lar sub-angular materials, but is less sandy and darker in colour, arising 
apparently from the admixture of chi)- derived from the wearing down 
of the Boulder Clay. The upper gravel seems to be of limited extent, 
but the lower gravel I believe to pass under the Boulder Clay, for 
there is an old pit of the same gravel near the brook on the north side 
of Bricket Wood, towards the Watford end. There is no Boulder Clay 
in this other pit, but the gravel presents the peculiarity of being con- 
creted in places into large brecciated and sandy masses bj' a 
calcareous cement. In this pit I found no organic remains ; 
but in the ballast pit I was fortunate enough to discover, in the lower 
gravel, a few pieces (but not sufficient to determine the species) of the 
tooth and tusk of an elephant. A workman, whom I afterwards spoke 
to on the common, told me he had found several bones in the lower 
part of the gravel, but none of them had been preserved. The lower 
gravel reposes upon an irregular surface of chalk, which is exposed 
at places at the bottom of the pit, which is now no longer worked 
and may, I understand, possibly soon be levelled. It is well worth a 
visit, and a longer search than I have been able to give. There is a 
station at Bricket Wood, but it is at the St. Alban's end of the wood, 
at a considerable distance from this cutting. 
