1878.] Superficial Gravels and Clays. 331 
the silt there is from 2 to 4 feet of the brown clay, with 
patches of pebbles at its base. 
The patches of gravel a , 2 are peculiar. They nearly 
always lie on an irregular surface of the beds below them, 
and look as if they had been dropped into the places they 
now occupy. Their place is often taken by an irregular line 
of pebbles. 
The bed of clay marked a, 1 in the sections is the wide- 
spread deposit so extensively dug for brick-making. It is 
entirely unstratified. Pebbles are scattered here and there 
throughout it ; in some parts they are scarce, in others 
numerous. These pebbles, by the partial denudation of the 
clay, are often collected into nests next the surface. The 
clay appears to have been originally distributed over the 
whole district, and to have been since partly removed by 
the action of the elements, the fine material of which it is 
composed and its position next the surface rendering it very 
liable to be washed away, especially on the slopes. When 
thin, it, with the irregular pebble bed at its base, forms the 
deposit named “ trail” by Mr. Fisher. No organic remains 
nor implements have been found in the brick-clay in the 
Ealing district. 
3. Brentford and Neighbourhood . — -The gravels and clays 
at Brentford were brought before the notice of geologists in 
1813, by Mr. W. K. Trimmer,* who described the occurrence 
of mammalian remains in the lowest division of the deposits. 
He stated that the uppermost beds were unfossiliferous, and 
that the bones occurred most plentifully at the base of the 
gravel, in hollows in the surface of the London Clay. In 
1849 Prof. Morrist described a section exposed in the con- 
struction of a branch of the South Western Railway, at 
Brentford, near Kew Bridge. This locality was not far from 
one of the pits described by Mr. Trimmer, and Prof. Morris 
again notices the absence of bones and shells from the upper- 
most beds, and the great abundance of the bones at the base 
of the lower gravel. Col. Lane Fox, in the paper I have 
already mentioned, has described and given figures of the 
sections exposed between Acton Green and the Brentford 
Road, and has shown very clearly the position of the mam- 
malian remains at and below the base of the gravel. 
My own observations have been made in various gravel- and 
sand-pits in the neighbourhood of Brentford, Chiswick, and 
* Phil. Trans., 1813, p. 131. 
f Quart. Journ. Geol. Soc., vol. vi., p. 201. 
