296 THE CARBONIFEROUS OF CAPE BRETON— GILPIN.. 
It is essentially white, but tinted and spotted with many 
colours. It oecurs in beds, often massive but frequently jointed 
in every direction. It is compact, or granular, minutely erystal- 
line, or fibrous and radiating. Crystals of selenite of a brownish 
or white colour frequently occur in it; they are isolated, or arran- 
ged in radiating groups, and sometimes give the rock a porphy- 
ritic appearance. The rock is frequently traversed by veins. 
filled with fibrous gypsum of various colours, or by large plates 
of transparent selenite. Layers and nodules of anhydrite and 
of limestone frequently oceur in the beds or divide them. Long- 
continued weathering roughens the surface of the gypsum, owing 
to the presence of silica as sand. 
These beds of gypsum are sometimes presented as immense 
lenticular masses, but they often extend for miles as an irregular 
cliff, reminding the tourist of a ruined marble wall. The vicinity 
of their outcrops is marked by the luxuriance of the grass, and 
by the vigorous growth of the evergreens which mask the conical 
holes formed by the removal of the gypsum through the action 
of the water drainage of the district. It may be remarked here 
that possibly some of the irregularities characterizing the out- 
crop of this rock may be due to the washing away of masses of 
salt. It is true that at present there is no evidence to show that 
such deposits existed, but the numerous brine springs issuing 
from this formation, and the common association of gypsum and 
salt, afford reasonable ground for anticipating valuable discoveries. 
of rock salt in Nova Scotia in the vicinity of the gypsum beds. 
LowER CoAL MEASURES. 
This term, as used by Sir William Dawson in describing 
measures such as those of Horton and Hillsboro, is applied, in 
speaking of this district, to strata of a quite different character. 
This, the lowest member of the carboniferous group, corresponds 
with the Bonaventure formation of Gaspe, and the basal conglo- 
merate of New Brunswick and Newfoundland is in this district 
of variable volume, and cannot be separated by any strict line 
from the overlying limestone formation, and it is Mr. Fletcher's 
opinion that in the districts surrounding the Bras d’Or Lake 
