We are now crossing the deepest part of the northern basin of the lake, where Dr. Mill found over 150 feet of water. The bottom rises, when we pass Hoathwaite boathouse on the right, to little more than 125 feet, and off Fir Island deepens again, attaining 184 feet half a mile farther down--making this the deepest of the lakes after Wastwater, Windermere, and Ullswater, as its 5-1/2 miles of length makes it the longest except Windermere and Ullswater. Its normal level is 143 feet above the sea, though it rises and falls in drought and damp weather as much as six feet. Of the form of its bed Dr. Mill says:--"If the water were reduced to sea level, there would remain two small lakes, the southern measuring one mile and a half in length, and a quarter of a mile in breadth, and having a maximum depth of 42 feet; the northern one, separated by a quarter of a mile, being only 9 feet deep, three-quarters of a mile long, and perhaps 200 yards wide at the most. Quite possibly the two might be connected by a channel, and give a long shallow lake of two and a half miles" (_Bathymetrical Survey of the English Lakes_, p. 39). This bank or dam between the two deeps is not caused by filling up from any stream like that at the steamer pier; it points to the fact, more strikingly seen in Windermere, that these long lakes, like most of the long valleys, are not mere troughs or grooves ploughed in the rock, but a series of basins, partly filled up with glacial débris, and partly joined together by glacial erosion, which broke and planed away the dividing barriers. Fir Island (formerly from its owner called Knott Island, now the property of Arthur Severn, Esq., R.I., J.P.) is low and close to the water's edge, hardly distinguishable except by its grove of Scotch firs from the rest of the coast. In very dry weather it becomes a peninsula, but usually a boat can make the circumnavigation, though there is risk of shipwreck on the sharp rocks to the landward side. Near it, beyond the road which winds prettily along the uneven and craggy shore, are the ruins of Copland's Barn; and above it the great larch woods of the Heald, on a noble slope of nearly 700 feet from the brow of the fell to the lake. The western shore is formed by the long and varied slope of Torver Common, down which runs the Moor Gill. At its foot, exactly opposite Copland's Barn, is the most extensive of the bloomeries, with the ruins of an old hearth still to be found. At last the continuous skylines are broken. On the left, a steep dingle runs up among rocks and woods to Parkamoor, a lonely farm on a bleak brow top; and on the right, the valley of Torver begins to open out, with glimpses of Dow Crags and the Old Man in a new aspect, showing their precipices boldly against the sky, and beneath them Sunny Bank and Oxness at the mouth of Torver Beck.