41 
had been greatly folded. Where the rock was composed of 
alternate layers of sandstone and slate the former had been 
converted locally into quartzite and the latter into micaceous 
schist. The friction also between the two had caused the 
conversion of the latter into well marked mica at the points 
of crushing. Other slides showed a subsequent series of 
strains which had produced “ cleavage-foliation planes ” 
running approximately at right angles to the contorted 
lamination planes. Others showed the change in structure 
produced by the crushing of the unyielding layers of sand- 
stone (now quartzite) into the comparatively plastic clay 
slate. 
Me. Stierup exhibited a small slab of the Flexible 
Sandstone of India.^' 
Mr. Stirrup afterwards showed some indented and frac- 
tured pebbles from the great conglomerate beds of the old 
red sandstone of Scotland, as exposed at Dunottar Castle, 
near Stonehaven, Kincardineshire. 
This conglomerate, or pudding-stone, is the lowest mem- 
ber of the old red series of rocks, and is found in various 
parts of Scotland, forming masses of great thickness and 
extent. 
The stones are water-worn and well rounded, of various 
sizes, and when in sitlX are embedded in what might easily 
be taken for ordinary mortar. 
The great tabular mass on which Dunottar Castle stands 
is from 120 to 150 feet above level of the sea, and it was 
from these great natural and precipitous walls of rock that 
the specimens exhibited were extracted. 
The interest which these pebbles excite, is due to the 
indentations which are found on them, and fractures which 
slab of flexible sandstone from India was exhibited, and a detailed 
description given to tlie Section by Mr. Plant, F.G.S., on the 16th February, 
1880. Proc., vol. xix., pp. 103 — 105, 
