12 N. F. Robarts on a 
decide upon the relative position of the two beds of sand and 
pebbles. 
The excavation of the fort showed that the whole surface of 
the chalk was honeycombed with pipes, and in an area of about 
thirty yards square the whole of the Clay with Flints appears to 
have sunk more or less into the underlying pipes. I should draw 
a ttention to the character of the Clay, which was of a peculiarly 
bright red, and free from any admixture of other rocks than 
Flint. 
The pipes were apparently absolutely conterminous, and could 
be traced in many places, not by the usual intervening pillars of 
chalk, but solely by the disturbance of the superior strata which 
have been let down into them. 
The greatest depth of the excavation was about 14 ft., exposing 
the side of a pipe, which evidently ran to a greater depth. The 
highest chalk between some of the pipes was about 6 ft. below 
the surface, but above the chalk divisions it was possible, by noting 
the different strata which had been let down, to trace the sides of 
the pipes, although the chalk between them had perished. 
In spite of the adjacent outlier of Oldhaven Pebbles being so 
near, in no instance was any of this pebble-bed to be found in 
the pipes, which in every case but two appeared to be lined at 
the side with green-coated flints, and filled up to the subsoil with 
Red Clay with Flints. In the two cases referred to, one pipe 
contained in its centre a reddish clayey gravel composed of very 
small tertiary pebbles with some small angular flints, which may 
have formed part of the Southern Drift, but I could not find in it 
any chocolate-coloured flints or implements, or Lower Greensand 
rocks. 
The other pipe contained, enclosed in the Clay with Flints, a 
buff-coloured clayey sand with a very few small greenish flint 
pebbles. evidently not derived from the Oldhaven Pebble-bed, 
unless the colour of the pebbles had been altered by the matrix 
in which the stones were lying, and thus their original colour 
had been lost. 
It was clear from the position of the sand in the centre of the 
pipe surrounded by “ Red Clay with Flints” that the sand had 
been superior to part of the Clay with Flints, and may have been 
derived from the sandy Oldhaven beds. If this was the case, as 
there were no Oldhaven Pebbles in the pipe, the Clay with Flints 
must either have been formed before the sand was deposited, or 
formed beneath it since the sand was laid down. 
But the supposition that this clayey sand, which is not unlike 
the sand on the north-west of the pebble outlier, was deposited 
on the Red Clay with Flints, and that the latter was of its 
present thickness, does not seem probable, as the great depth 
of the surrounding clay would, in a comparatively narrow pipe, 
