Having thus completed his inspection of the left-hand branch of the Imperial Cave, the visitor returns to the junction, passing through all the chambers previously noticed in it excepting the Architect's Studio and the Bone Cave, and proceeds to explore the still more wondrous and beautiful works in the right-hand branch. THE SUBTERRANEAN RIVER. The first object of interest in the right-hand branch of the Imperial Cave is the Subterranean River, which runs at the bottom of a fearful chasm about 50 yards from the point where the two branches bifurcate. After having wandered through marble halls and crystal palaces, and bowers where "rural fays and fairies dwell," the course seems rather gloomy. But attention is attracted by some curiously-shaped nodules, like those found in a part of the Arch Cave, and by basins with thin laminated sides slightly corrugated. These specimens reveal the secret of the construction of the pretty reticulated mounds, which give such a charming effect to several of the most regularly formed features of the caves. To complete the process, the sharp parallel lines which form a succession of little equidistant ridges require only to be smoothed off by a gently flowing film of water, and to receive a coat of colouring derived from clay or oxide of iron. This part of the branch, therefore, should not be passed through hurriedly, for it is instructive. [Illustration: THE UNDERGROUND RIVER AND ITS REFLECTIONS.] The road is fairly good, although the arching is low. Those parts, the narrowness of which formerly made progress difficult, have been enlarged, but a pretty natural bridge has been carefully preserved. The halt is at the end of a wire ladder bent over a cliff, which forms one side of an immense gulf, where perpetual darkness broods. Here the visitor has a more ungraceful task to perform than that of the cursed serpent, for he must recline face downwards and "progress backwards" until he assumes the form of an obtuse angle, with one line over the precipice. Then he has to use his legs pretty much as an octopus uses its tentacles, to gain a footing on the ladder, which descends about 50 feet on the chasm side of the angle. Having found the first rung he feels happy, but not sufficiently hilarious to slide like a lamplighter. He grips the side wires carefully, takes heed to his steps, and goes down slowly. When he has descended a little way, the dim candle-lights above appear to be far distant, and when he is 20 or 30 steps down they look like glowworms. The journey, however, is not perilous to persons who possess a fair share of agility and nerve. It is frequently performed by ladies, of whom the guide is specially careful, preceding them and keeping just below them on the ladder. As this is, perhaps, the most interesting of all the cave sights, it is desirable that some easy mode of descent should be provided, such as a skip like those employed in mines, or a lift made by machinery to work as easily and