It was now past three in the morning. Tired and battered to the point of exhaustion, but delighted with an exploration that far exceeded in interest all we had looked for, we returned to the cave mouth. An unpleasant-looking bull which had with great suspicion watched us make our nocturnal entry into the regions below had, greatly to our relief, got tired of waiting, and the coast was clear. Out of the everlasting silence and the shadows, lit so rarely by the glare of the magnesium and the beams of the limelight, we returned again, with the surprise that never fails, to the light of the heavens. Dusk was on the far-extending moors and hills, daylight was creeping on over the sky, a pair of larks saluted us with a hilarious song. Our driver was soon awake at the little inn, two furlongs away, and in the freshness of the morning we crawled down the break-neck road to Appletreewick, Bolton Woods and the Wharfe growing in light before us; and then at an exhilarating pace rolled up the dale to the Red Lion at Burnsall. SWALLET-HUNTING IN DERBYSHIRE "GIANT'S HOLE" AND "MANIFOLD" Between Sparrowpit and the head of the Winnats the old road from Chapel-en-le-Frith to Castleton skirts what is, geologically, one of the most important localities in Derbyshire. It runs along the side of a shallow upland valley, about 1200 feet above tide-level and two miles long, which is bounded on two sides by the curve of Rushup Edge and on the other two by Elden Hill, Windy Knoll, and other Limestone acclivities. One of the great faults of the Pennine chain traverses this valley longitudinally, the Yoredale strata having been thrown down to the level of the Limestone, so that the middle of the valley is the boundary between the Yoredale rocks, shale grits, and milestone grit on the north, and the Limestone plateau of Mid-Derbyshire on the south. The valley is completely encircled by higher ground; there is no egress for streams on the surface. Accordingly other modes of drainage are to be looked for, and they will be discovered in a numerous series of swallets situated along the line of the fault, the water that runs over the impervious shales perforating the Limestone as soon as it comes in contact with it. This shallow valley, in fact, is the gathering ground for the waters that pour into the abyss of the Speedwell Cavern, traverse Peak Cavern, and make their way to the open air at Russet Well and other springs at Castleton. That such is the case has long been proved by observations of the temperature and colour of the waters, and by tracing chaff and other things thrown into the upland streams. But there exist hardly enough data to establish the theory of the French speleologist, M. Martel, that Peak's Hole Water comes from Perryfoot, and the water of Russet Well from Coalpit Mine, near Sparrowpit. All that is definitely known is that these waters run through the massive Limestone for distances varying from two to three