THE CARBONIFEROUS OF CAPE BRETON—GILPIN. 293 
nodules, and the more argillaceous beds are crowded with fossils, 
chiefly ferns. Many trunks of erect and prostrate sigillariz, 
with roots attached and grown into the coal, are seen in these 
shales; they have been observed nearly five feet in thickness, 
but those which have come under my notice have not usually 
exceeded two feet in diameter. The term marl is applied here 
to beds not necessarily caleareous, but to red and green shales 
which crumble readily on exposure. Sandstone beds, gray and 
white in colour, and often fifty feet in thickness, are met at fre- 
quent intervals, and nearly always occur a few feet above a coal 
bed. Many of the sandstone beds are calcareous, and are then 
flaggy micaceous, and sometimes ripple-marked. 
Almost invariably underclays highly charged with stigmariz 
roots and rootlets, and from a few inches to eight feet in thick- 
ness, form the floor of the Coal seams. Ina few instances Coal 
seams rest directly on thin beds of fossiliferous limestone, and 
in one instance the floor is sandstone. Beds of black bituminous 
limestone, from a few inches to three feet in thickness, have 
been observed about the middle of the section. The physical 
characters of the coal beds will be referred to in connection with 
the analyses to be given in the appendix, and it may be remarked 
here that they resemble in many points those of the Durham 
district in England. 
The division line between the Millstone Grit and the Productive 
Measures is an arbitrary one, and, as marked on the Geological 
Survey maps, is considered by many as encroaching on measures 
which may fairly, so far as their coal contents are concerned, be 
considered productive. This opinion is strengthened by the fact 
that a large collection of plants from the Cossit pits, a short dis- 
tance east of Sydney town, at a horizon considered low down in 
the Millstone Grit, were reported on by Sir William Dawson as 
distinctly marking the productive horizon. Further investiga- 
tions may show that the distinctions at present laid down as 
separating the upper part of the Millstone Grit from the Coal 
Measures are due more to local conditions of deposition, which 
have modified the Coal Seams and their encasing strata, than to 
any change of the distinctive features of the preceding horizon. 
