132 
The gravel consists of flints rolled and sub-angular small 
rounded Chalk pebbles, Forest marble, Coral bed of Inferior 
Oolite, White and blue Lias. Red and pinkish sandstone, 
fine and coarse grained yellow saccharine sandstone, both from 
the Millstone grit probably. Mountain limestone and ferruginous 
nodules. Ina band of sand here and there overlying the clay, 
land and freshwater shells (Bythinia, Pisidium amnicum and 
Zonites,) were found a few inches above the clays, and below the 
Mammalian bed. 
We now pass on through this gravel which occupies a trough- 
like depression in the clays, the deepest part of the trough 
coinciding with the highest part of the knoll and the thickset 
deposit of gravel, and come to thick beds of light-blue clay with 
a patch or pocket of gravel resting on them just before entering 
the tunnel under Bloomfield Place. Aneroid measurement gave 
this gravel a height of 152ft. above the river, or 63ft. above the 
Moorfield cutting. The embankment of clay is here about 20 or 
30ft. in height, and has running irregularly through it about 
midway a hard compact blue irony limestone stained reddish in 
the centre. Entering the tunnel, which is cut out of the Sands 
principally, we find about 50 yards from the entrance the sleepers 
for the rails resting on a large block of stone, Oolitic and 
ferruginous outside, Tin. to 12in. thick, evidently in situ. From 
this I obtained a specimen of Ammonites serpentinus characteristic 
of the Upper Lias. This block rested on the light-blue clays. 
Now comes the question,—What are these clays? Are they the 
Upper clays of the Lower Lias (they certainly are not the Lower 
clays of the Lower Lias), or are they Upper Lias Clays, which 
from a thickness of 200 feet on the Yorkshire coast are said to 
thin out in our neighbourhood so rapidly, that when exposed 
(which is rarely the case) they are “barely traceable in a band a 
few feet thick.” If this is so (vide Phillips Geol. of Oxford, &., 
p- 117), which I am inclined to think possible, then we have here 
one of the best exposures of Upper Lias which have yet been 
