"Torsa is a pleasant fertile single farm of about 250 acres. It provides excellent pasturage for cattle, and, unlike the neighbouring islands, almost its entire surface is capable of cultivation. At one time it was the abode of a crofting population of eleven families. The land was let on the old system of "run-rig," and after the lapse of one hundred years the narrow plough ridges, about six feet broad, are quite visible, giving a ribbed appearance to the long slopes of green pasture.

At the north end of Torsa, built upon a steep ridge of trap rock, are the ruins of a medieval Highland fortress: it is called Caisteal nan Con (the Dogs' Castle). It is supposed to have been a hunting-seat of the Lords of the Isles; but more than likely the name is derived from a sobriquet often applied by their enemies to the powerful Clan MacLean-Clann Illeathain nan Con; and although Pennant, MacCulloch and others state that the castle belonged to the MacDonalds, tradition clearly relates that it was built by the MacLeans, who, during the sixteenth century at least, held the lands of Luing, Shuna, and Torsa in feu from the Earl of Argyll. The castle displays the remains of two square towers, with a circular work at one corner. The walls are neatly fitted into the crevices of the rock upon which the castle stands, so that they form one continuous scarp, making an attack by escalade impossible."