217 
whole of this table-land is a trail of drift gravel composed of 
pebbles of quartz, trap, and haematite iron ore, which may be 
also traced down the slopes of the hill to the valley below. 
Viewed from this new aspect of the case, it is highly probable 
that the flakes and the gravel of the Cavern have been derived 
from this trail of drift, and this probability becomes almost a 
matter of certainty when we consider that the flakes are asso- 
ciated with the same kind of gravel and nodules of iron ore, 
both on the outside and the inside of the Cavern. 
I will further confirm this connection by an example easy ot 
access, and open to daylight inspection. The limestone of the 
Hoe, the public promenade at Plymouth, is geologically the 
same as that of Brixham ; at the south-east corner of the Hoe, 
near the flagstaff, it forms an inland cliff, where a fissure from 
one to three feet wide extends vertically the full height of the 
face of the cliff, which is about thirty feet. This fissure is filled 
to the top with loam and drift pebbles, and a trail of similar 
pebbles is found scattered over the surface of the rock above 
the cliff, showing an absolute connection between the drift 
gravel on the surface and in the fissure. 
Thus we obtain the most complete evidence which the nature 
of the case admits, that the shattered flints found in the Brix- 
ham Cavern were derived from the trail of drift on the table- 
land above, and were washed into the Cavern with the loam and 
gravel in which they were found \ and that the so-called flint 
knives” are only subsoil flakes, which may be found by thou- 
sands scattered through the soil in various parts of Devon and 
Cornwall. . . _ T1 ^ . ,, . . 
Here, however, a further question arises. V^hat is the origin 
of these subsoil flakes ? In a paper which this society did me 
the honour to reprint,* I have shown that there is good 
evidence to prove that these flakes have been formed by natural 
causes, and that they can be traced backwards along the line of 
drift to the natural home of the flint in the chalk ; and to the 
arguments there adduced I will only now add, that the rela- 
tive proportion of flakes found in various caverns corresponds 
closely with their abundance or paucity in the adjoining dis- 
tricts. Thus in a cretaceous country, like that of the depart- 
ments of the Dordogne and Charente, they are found by 
thousands in the caverns. In others, on the line of the flint 
drift, the flakes become scarce as the caverns are near to or 
removed from the influence of the drift. This point is well 
* See Journal of Transactions of the V ictoria Institute, vol. viii, p. 
