106 CARBONIFEROUS OF CAPE BRETON—GILPIN. 
are the same seams, although somewhat changed in character and 
size as they range over some twenty-five miles of country. The 
seams are identified by the thickness of the masses of interven- 
ing strata, some peculiarity of roof or floor, ete. ete. The Geo- 
logical Survey have tabulated the seams of the different districts, 
and as their conclusions do not appear to coincide with the 
opinions of any of the critics, it may be assumed that they are 
pretty near the mark. The question, however, is one of geological 
rather than of economic interest, as the coal seams all vary 
slightly in their quality at intervals of a few miles. 
Coal. 
Having outlined the distribution of the Carboniferous of Cape 
Breton as laid down on the excellent maps of Mr. Fletcher's 
reports to the Geological Survey, the next task is the considera- 
tion of the minerals characterizing it. The principal minerals 
are coal, gypsum, limestone, and iron ore. As the first named is 
the most important, I venture to dedicate this paper to its con- 
sideration, and propose to describe the remaining minerals, 
together with those found in the other geological horizons, at a 
future time. This will prove more convenient for reference, as 
several of them, notably the iron ores, are common to several 
ages. In this island coal beds are found most abundantly in the 
productive measures, but there are important deposits in the 
millstone grit. There are also beds of coal in measures referable 
possibly to the upper coal measures, and in the Richmond district 
coal occurs apparently in conjunction with the marine limestone 
measures. Examples are not wanting in other countries of 
valuable deposits of coal in these divisions of the Carboniferous, 
but so far as our information goes we are not warranted in look- 
ing to them as important sources of this mineral in Cape Breton. 
T have already alluded to the fact that it is difficult to draw 
with distinctness the line separating the productive from the 
millstone grit measures, and will therefore consider the coals 
without regard to their geological position, a factor little affect- 
ing their composition. 
Speaking in general terms, the Cape Breton coals are bitumi- 
