REPORT OX THE EXPLORATION OE BRIXIIAM CAVE. 
5G7 
of quiet succeeded, during which a first bed of stalagmite was deposited immediately 
upon the bed of shingle. Remnants of this old layer of stalagmite, with the pebbles 
forming the top of the original shingle bed attached to its under surface, were found 
adhering to the sides of the cave, 3 to 4 feet above the second or later stalagmite floor. 
The breaking up of this layer of stalagmite and the lowering of the surface of the shingle 
bed to the extent of from 6 to 10 feet, was accompanied by a complete change in the 
state of the cave (see figs. C, D, E, Plate XLII.). 
These effects may have been produced either by an irruption of water carrying away 
part of the shingle, and so undermining the stalagmite, or by the breaking up of the 
stalagmite, and the settling down of the shingle deeper into the fissures, by earthquake 
movements. We are disposed to adopt the latter alternative ; for Mr. Pengelly has 
remarked that the surface of the shifted shingle, instead of presenting a depression in 
the middle with edges rising up to the sides of the passages, is, on the contrary, 
raised in the middle and is depressed on the sides — a form which is hardly compatible 
with the action of flowing water, but rather accords possibly, in our opinion, with the 
results of the vibrations and settlements caused by earthquake action. Prom this 
moment new conditions of the cave commenced. Instead of fissures receiving shingle- 
bearing streams, and water more or less constantly flowing through the cave, we now 
come to a period when the cave was habitually dry, though it remained subject to 
occasional floods from the main stream of the Brixham valley, then in the course of 
excavation. The flood-waters charged with silt deposited the cave-earth gradually 
during each successive inundation, like as, in other districts, the loess was deposited 
during the river-floods in the more sheltered spots of the main and lateral valleys ; while 
during the whole time blocks and fragments of the old high-level stalagmitic floor con- 
tinued to fall in more or less abundance. 
We admit the difficulties of the case, — of realizing how, in so short a course as the 
Brixham stream had, and with so small an area of drainage, a sufficiently powerful body 
of water could be collected to excavate such a valley ; but it is a difficulty which meets 
us in many valleys of denudation when we contemplate the small causes at present in 
operation with the comparatively gigantic effects produced. We can only account for 
it, as we have done elsewhere, on the hypothesis of an intensely cold climate, of which 
we have such abundant evidence, accompanied by a greater rainfall, by spring floods 
of great power such as now occur annually in all arctic regions, and by ice action. 
It is further possible that a slow movement of elevation was in progress during 
this period, which counteracted the loss of gradient in the lower part of the valley 
caused by the process of denudation. The submarine forest of Torbay, which after- 
wards grew on land now 30 feet beneath the sea, shows the entire rise at one time 
to have been 40 feet or more above the present sea-level, or 70 feet or more above 
the level of the old raised beaches, to which extent the fall of the stream was then 
increased. 
The breaking up of the first and original bed of stalagmite, and the lowering of the 
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