Where the rays of light pierce through the night to its rocky boundary indistinct, irregular lines can be seen like the ribs of a skeleton, and it is easy to conjure up all sorts of uncanny shapes, from hobgoblins to anthropophagi. The only sounds audible, or apparently audible, are the quickened respiration and the throbbing of the heart. When the voice is raised its effect is strange, and there is no responsive echo. Darkness and silence dwell together. After spending a few seconds--or minutes--in their company, the curator lights his magnesium lamp, and the visitor finds himself in the precincts of "The Cathedral," in the centre of which is a large stalagmite. The roof rises to a height of about 300 feet, 70 feet loftier than Canterbury Cathedral or Notre Dame, and within 100 feet of the altitude of St. Paul's! The walls are composed of limestone, terraced with tier upon tier of stalagmites brought into bold relief by the gloom of innumerable fantastically-shaped recesses. The preacher is Solitude; his theme is "Awful Stillness." Wandering through the nave to the south, the visitor walks over caves not yet opened, but the existence of which can be proved by dropping little pebbles into dark recesses and listening to the percussion on floors more or less remote. In an aisle of the Cathedral leading to the Music Hall, there is another grandly-arched cavern with a steep descent into an abysmal depth. Here on the one side are numerous stalactites, white as virgin snow, and on the other similarly-shaped formations of carbonate of lime tinged with oxide of iron--some of them so deeply as to present the colour of a boiled lobster's crust. This is a favourite clustering place for bats, and numbers of these membranous-winged quadrupeds may be seen snoozing together on the roof. THE MUSIC HALL.