On my expressing a desire to examine the underground aqueduct, Sala led the way to one of the man-holes situated a couple of kilometres to the north, near the upper end of the tunnel. Producing a palm-fibre rope from under a ledge in a cliff hard by, he attached it to a log placed across the mouth of the shaft. There was a hot, steamy current of air ascending from the man-hole, the interior of which was as black as night. Sala had, however, provided candles and matches, and when he reached the bottom and shook the rope as a signal to me to follow, I could see a tiny speck of light in what seemed to be the bowels of the earth. Fortunately I had had a good training in the Cornish and Welsh mines at home, so that the prospect of a descent by the rope did not worry me in the least, and after scrambling into the shaft I went carefully down hand over hand. The shaft, rectangular in cross-section, and beautifully cut through the solid sandstone rock, measured roughly 1½ metres by ¾ of a metre, tapering gradually downwards. The first few metres, sunk through the down-wash forming the bed of a valley, were carefully built in with blocks of limestone, the bottom layer resting on the solid rock below. Rough footholds on opposite sides of the shaft facilitate the descent, and when nearing the bottom, as the rope stretched and contracted like elastic in a most unpleasant manner, I was glad to avail myself of their assistance. The shaft, which I afterwards found to have a depth of 40·3 metres (132 feet), goes down perpendicularly, and when the bottom was reached, I found myself standing in a gently flowing stream of water, which I knew continued its underground course for at least 2 kilometres to the south. The tunnel itself is distinctly coffin-shaped in cross-section, being widest near the roof, and tapering downwards. Its average height is about 1½ metres, the mean width near the top being about 60 centimetres—_i.e._, it measures roughly 5 feet by 2 feet. In some places it is even narrower, so that a man of average stature not only has to keep his head very much bent, but is also forced to progress sideways if he wishes to make his way along the channel. The place was so sultry, and the cramped position I had to assume so tiring, that I had soon had enough, and groped my way back to the base of the shaft. As I had anticipated, the ascent proved considerably more difficult than the descent, and I was not sorry when I regained the surface. After the heat of the shaft and the exertion of climbing, the outside air, despite the fact that it was an exceptionally hot day, felt bitterly cold, and the rapid evaporation from our perspiring bodies chilled us to the marrow.