42 
penetrate them; some having been completely fractured, 
and afterwards re-cemented while in their original position. 
This peculiarity is not found in all the conglomerates of 
this age, as in many districts where these rocks occur in 
force, indented and fractured pebbles are never found. 
Slight cracks or faults may be seen traversing the face of 
the cliff, but the amount of displacement is often exceedingly 
small, as demonstrated by the disjoined fragments of some 
of the stones. 
These conglomerates are formed for the most part of the 
hardest rocks, granites, quartzites, &c., siliceous rocks having 
probably the preponderance, yet we find that some of these 
pebbles have been squeezed one into the other, the pro- 
tuberance of one having formed the indentation of the other, 
which, moreover, often shows signs of fracture and re- 
cementation. 
That these rocks have been subjected to immense pressure 
these pebbles give evidence, and that a gigantic shearing 
force has been exerted is also manifested by the cloven stones. 
An examination of the pebbles does not confirm the 
hypothesis that these rocks have been buried under thou- 
sands of feet of superincumbent strata, where the pressure 
must have produced heat enough to render the rocks plastic. 
The mineral structure of the rock does not appear to be 
altered, and the present cracked and fractured condition of 
the pebbles does not seem to accord with the suggested 
plasticity. 
