1847.] LYCETT ON THE OOLITE OF MINCHINHAMPTON. 185 
are extensively used for roofing. In the preparation of the tiles no 
exposure to frost is necessary, light dressing with the hammer being 
all that is required: they form a covering more durable than the 
Stonesfield slate, but heavier and less neat. These laminated tile- 
stones are sprinkled over with small oysters, pentacrinal remains, 
spines of Echini, ossicula of Ophiura, &c. 
Connected with the forest marble a local deposit occurs of a cu- 
rious character ; it consists of a bed of thin, brashy, but very hard 
calcareous stone, full of irregular holes, forming masses sometimes 
very large. One of these has been placed erect, about a mile from 
the town, and is known by the name of Longstone, a sepulchral mo- 
nument it is supposed of great antiquity. The extent of this stratum 
is unknown, but it certainly covers very many acres, and is extracted 
for out-of-door ornamental purposes, on account of the grotesque forms 
which it assumes. Unlike other oolitic stones, the only change which 
it experiences by exposure to the weather is that it becomes somewhat 
whiter. Its singular structure would appear to be owing to the 
forcible escape of gases from beneath while the stratum was of a soft 
or pasty consistence. 
No positive line of separation can be drawn between the forest 
marble and great oolite; the shelly beds of the former gradually 
change to thin-bedded sandstones nearly destitute of organic remains ; 
stems of Apiocrinites, however, may be traced throughout the middle 
subdivision. At the upper part of this series, or about 90 feet 
above the Fuller’s earth, is a bed from 14 to 2 feet in thickness, em- 
phatically termed the ‘limestone bed’ ; which is distinguished from 
all the associated strata by a remarkable uniformity of thickness and 
mineral character over a large area. It may be described as a very 
hard, homogeneous, cream-coloured rock, occasionally containing 
shells which agree specifically with those of the uppermost beds of 
building stone or planking. It has been traced from the town of 
Minchinhampton on the west to a deep section made by the Swindon 
and Gloucester Railway, close to the east entrance of the smaller of 
the two Sapperton tunnels, a distance of five miles; where it appears 
near the middle of the section. It is sometimes burned for lime, 
which is moderately good, though more impure than that obtamed 
from the carboniferous limestone. 
The third subdivision or weatherstone is exposed in many openwork 
quarries situate to the west of the town and on the northern side of 
the vale of Brimscombe or Chalford; the whole of the beds are 
extracted down to the Fuller’s earth, The mineral character of the 
weatherstone beds is found to vary considerably within a short di- 
stance, a change being sometimes observable even on opposite sides of 
the same quarry. The description of any one section will therefore 
afford only a very general and distant notion of a similar section in 
another locality. ‘Taking for example the largest quarry on Min- 
chinhampton Common, one mile west of the town, we there find the 
upper part to consist of thmly-lamimated stone, the laminz being 
irregular and often rising at a high angle, 5 or 6 feet in thickness ; 
this should probably be referred to the middle subdivision. 
