34 CARBONIFEROUS OF CAPE BRETON—GILPIN. 
the shores of West Bay, at Port Hood, etc., but they need not be 
noticed in this brief sketch. 
This formation presents everywhere beds of limestone and 
gypsum, with marl shales, sandstones and grits, of various colours, 
frequently gray or red. 
The gypsum deposits are of every conceivable variety of 
colour, texture and quality, and frequently extend for miles. 
They often give rise to saline springs and mark the ground with 
funnel-shaped holes. The limestones are in equal variety, and 
at some points carry the fossils characterizing the formation. 
Little use is made of these minerals, nature having scattered the 
former everywhere ; while a few bushels of the latter meet every 
requirement of the local architect and mason. The student will 
frequently notice these measures running in long tongues and 
spurs beside some brook in large deep valleys of the Pre- 
Cambrian felsites and syenites, thus bringing into close con- 
nection the valleys of three epochs of countless years. There is 
first the Pre-Carboniferous valley eroded in the felsites. In 
this was deposited the marl, limestone and gypsum, and finally 
we have geologic history repeating itself, and a glen worn out in 
them in their turn by some brook bearing a highland name. 
At many points the sub-divisions of the Carboniferous pre- 
sent signs of unconformability, but this cannot be settled in 
many cases, as there are frequent faults and small undulations, 
which when accompanied by great erosion, made unequal by the 
varying resistance of limestone and gypsum, and marl, yields 
dips of uncertain value. Generally speaking, however, the 
sequence in passing from north-west to south-east is fairly 
recular. 
No estimate is given by Mr. Fletcher of the thickness of 
these measures, except in connection with the Port Hood mines, 
where he has measured one section lying above the gypseous 
strata, which is 3370 feet thick. Owing to the inter-section of 
the district by the outliers and ridges of Pre-Carboniferous 
rocks and to the deposition of the Carboniferous in their hollows, 
ete., it is doubtful if any exact measure of their volume will be 
arrived at. 
