The electricity is to be generated by a small Edison dynamo, with which accumulators of the Elwell-Parker type will be kept charged, so that at all times there will be a supply available for lighting the lamps. It has not yet been determined whether to use steam or water power, but it is thought likely that sufficient of the latter may be secured in the vicinity of the caves to work a turbine, and thus produce the necessary energy. CHAPTER XVI. THE HELENA CAVE. Leaving the Margherita Cave by a descent of five steps, and travelling north-west about ten yards through a festooned hall, the Helena Cave opens to view. It was named in 1880. Helena is the prenomen of Mrs. Hart, whose husband accompanied Lieutenant-Colonel Cracknell on his visit to the caves, and took photographs of some of the chambers, when for the first time they were illuminated by electricity. Mr. Hart was connected with the photographic branch of the Government Printing Office. The pictures then produced, although large and fairly good, are not equal to some more recent photographs taken when the chambers were illuminated by the magnesium light. [Illustration: THE HELENA CAVE.] The Helena Cave is about 60 yards long, 15 to 20 feet high, and varies in width from 20 to 50 feet. For stalactitic splendour it will bear comparison with the most magnificent of the caves. There are columns like the trunks of stately trees, covered with rough formation resembling coarse bark. Coralline masses droop laden with myriads of cells. In the recesses are stalactites perfect in shape--crystal, and alabaster set off by others coloured like ferruginous sandstone. Lovely grottoes and decorated rock ledges abound. In one or two instances joined stalactites and stalagmites form pillars with bunches of formation all about them like stony efflorescence. Several steps lead into a recess, the floor of which contains basins made by the action of water. The formation throughout is remarkable for its lavish ornamentation and purity. Among the grand cornices is one weighing about half a ton, formed in such a manner as to resemble great bunches of grapes, like those brought from Eschol by the Hebrew spies to illustrate their report on "the promised land." In other parts are small clusters like vine produce growing _en espalier_. It seems as though in these subterranean sunless bowers nature had by some subtle process striven to reproduce in stone the fruits and flowers of the sunned surface, clothing them in pure white and sombre grey, and endowing them with charms as sweet and mutely eloquent as the fragrance of the Cestrum nocturnum, or the cold beauty of a night cactus bloom which caresses the moonbeams or wantons in the stellar light.