For a considerable time I have taken much interest in the question of the origin of the narrow and deep valleys in the Carboni-ferous Limestone district of Derbyshire, and have carefully recorded whatever seemed to explain their formation. So far I have never met with more striking facts than those to be seen in Deep Dale, about three miles in a direct line E.S.E. from Buxton. I estimate the depth of the valley at about 100 feet, and its width at from 100 to 200 yards. At a distance of about a mile from the Bakewell road there is a cavern, which is especially conspicuous on the east side. Its entrance is about 6 feet high, 20 feet broad, and 40 feet above the bottom of the valley. It extends nearly horizontally for about 30 yards, and then descends to a lower level, where I did not further examine it. On looking from the entrance to the opposite side of the dale I was surprised to see what appears to be a continuation of the same cavern. The entrance on that side is at about 80 feet above the valley, and is so much blocked up with detritus that one can only examine it for a space of 10 yards. Taking, however, all the facts into consideration, it appears to me that at a very remote period a subterranean stream flowed continuously along these two caverns, from west to east. There is abundance of suitable gather ground on the west side which even now has no well-marked surface drainage, and from which much of the water probably escapes by a subterranean course, ending in the large spring in the main valley, by the road-side below Kingsterndale.