CARBONIFEROUS OF CAPE BRETON—GILPIN. 27 
circuit of the district now under consideration. Its length is 
about eighty miles, and its maximum width from Mabou to the 
Grand Narrows about thirty-five miles. It 1s composed almost 
exclusively of Carboniferous measures with a few protruding 
ridges of Devonian and Pre-Cambrian strata. The largest of 
these ridges forming the Craignish and Whyhogomah hills 
begins near Plaster Cove, in the Strait of Canso, and runs north- 
easterly to Whyhogomah; its width at the Strait of Canso being 
about ten miles, but narrowing to an average of about five miles. 
Near the Strait of Canso it is largely Devonian, then Pre- 
Cambrian felsites, ete, are met, followed by the associated 
crystalline limestones, most generally known in connection with 
the Whyhogomah iron cres. Scattered areas, small in extent, of 
felsites and limestones, are met at the head of, and near the eastern 
shore of Lake Ainslie, and connect with the main body first 
referred to along the divide between the Margaree and the St. 
Patrick’s Channel watersheds. The highlands of Cape Mabou, 
and of the Malagowatch Hills, and some small outliers along the 
north side of St. Patrick’s Channel may complete our reference 
to these pre-Carboniferous measures. 
It may be remarked here that throughout Cape Breton the 
older and harder rocks in ridges of varied size and outline have 
a general north-east and south-west course, and are higher than 
the newer carboniferous strata which dip, roughly speaking, 
away from them, forming wide valleys. The traveller will 
readily recognize these features in the stern hills of Boiesdaie, 
St. Ann’s, Coxheath, Mira, Marble Mountain, etc., as compared 
with the valleys of the Sydney, Middle and Margaree, as well as 
of the Dennys and Inhabitants Rivers. 
Taking the productive and millstone grit measures together, 
they are to be looked for on the Gulf shore, and apparently 
at one time formed a belt continuous, at least from Judique to 
the Cheticamp River, a distance of about sixty miles. Now 
they form four narrow strips, separated by the Pre-cambrian of 
Mabou and by the Lower Carboniferous horizons of Mabou 
River, Broad Cove and Grand Etang, their width nowhere 
