Cape Breton, an island lying between lat. 45° 27' and 47° 5' N., and Ion. 59° 40' and 61° 40' W., belonging to the province of Nova Scotia, from which it is separated on the S. W. by the gut of Canso, 1 m. to 1 1/2 m. wide. The N. E. extremity of the island, Cape North, is 73 m. from Cape Anguille, the S. W. point of Newfoundland; its greatest length from N. to S. is 100 m., greatest breadth from E. to W. 85 m.; area, 3,120 sq. m.; pop. in 1871, 75,483. The island is very irregular in shape, and is nearly divided into two parts by the Bras d'Or, an inland sea with a narrow outlet. At the entrance lies Boulardrie island, between which and the main island on the S. W. is Little Bras d'Or. The Bras d'Or is 55 m. long and 20 m. wide, and varies in depth from 70 to 300 ft. The coast is for the most part rocky and elevated, and indented by numerous bays and inlets, particularly on the E. and S. The chief harbor is that of Sydney, at the head of an inlet 7 m. from the sea, on the E. coast. There are several other harbors on the E. and S. coasts. The principal harbor on the W. coast is that of Port Hood. Madame island, on the south, is reckoned a part of Cape Breton, from which it is separated by a narrow inlet called St. Peter's bay.

Cape Breton is divided into the counties of Cape Breton, Inverness, Richmond, and Victoria. The chief town is Sydney, with 2,900 inhabitants. The inhabitants of the island are mainly French Acadians, Scotch and Irish immigrants, and their descendants. The Scotch are mostly from the Highlands and the western islands. There are also 200 or 300 Indians. The island contains several fresh-water lakes, the principal of which are Lake Margarie, in the N. W. division, 40 m. in circumference, the outlet of which is by a river of the same name 15 m. long, and Grand lake and Mire river or lake, in the S. division. Mire lake receives the waters of Salmon river, which flows from the west. Several rivers fall into the Bras d'Or, the most important of which are the Bedeque and Wagamatcook on the north, and the St. Denis on the west. Cape Breton terminates a low mountain range, traversing Nova Scotia from S. W. to N. E., and contains much high land. The climate is subject to considerable extremes; the mean summer heat is 80°, while in winter the mercury often falls to 20° below zero. On the E. coast the summers are usually dry; on the W. coast they are generally more moist. Mica slate, clay slate, syenite, and primitive trap are found in all parts of the island.

Gypsum is abundant, particularly along the shores of the Bras d'Or; iron ore is also found, and there are several salt springs. The most important mineral is bituminous coal, which is found in the W. part of the island, but is most abundant in the S. E. division. In 1865 there were 18 coal mines in operation, and 429,175 tons were obtained. The forests consist of hemlock, black and white spruce, white and red pine, oak, beech, birch, and maple; but the timber trade has been gradually diminishing. The chief agricultural products are wheat, barley, oats, potatoes, turnips, hay, butter, and cheese. The inhabitants also carry on domestic manufactures of cloth and flannel. Fishing is one of the chief industries, the coasts and harbors abounding with fish of various kinds. Large quantities of cod, mackerel, and herring are taken. The chief exports are timber, fish, and coal; the chief imports are British manufactured goods, corn and meal, and colonial products. A majority of the inhabitants are Roman Catholics; Scotch Presbyterians are also numerous, and there are some Episcopalians. Cape Breton sends five members to the Canadian house of commons. - The first settlement in the island was made in 1712, by the French, who called it Isle Royale, and who eight years afterward constructed the fortress of Louisburg, on the S. E. coast.

It was taken from them by the colonists of New England in 1745, and was finally ceded to Great Britain in 1763. In 1784 Cape Breton was separated from Nova Scotia, to which it had previously been politically united, but in 1819 it was reannexed. In 1856 a telegraphic cable was laid across the gut of Canso, connecting the island through Nova Scotia with the telegraphic system of the United States. A land line, connecting with the cable on the Cape Breton side, was constructed through Port Hood to A spy bay, on the N. E. coast of the island; and in the same year a cable was laid across the entrance to the gulf of St. Lawrence from Aspy bay to Port au Basque on the W. coast of Newfoundland, while a land line connected this point again with Heart's Content. Since the landing of the first Atlantic cable in 1866, the line across Cape Breton has formed part of the intercontinental system.