The Cave of the Moa is in a limestone hill, with two openings, one towards the north-east and the other towards the south-west. The north- east opening has evidently been caused by the falling in of the roof, and is apparently of no great age; the south-west entrance is 14 feet high and 10 feet broad, and covered over with trees and bushes. The cave is 165 feet long, the greatest breadth 28 feet, and the height 60 feet. The roof is oval, and numerous stalactites drop gracefully from it, giving a cathedral-like effect to the whole. One part of the floor is covered over with calcareous spar, another part with a large deposit of soft stalagmites, and the part of the floor furthest distant from the south-west opening is covered with earth, limestones, and mud, which appear to have fallen down when the roof of the cave gave way, which now forms the north-east opening. It is under this earth, and the soft deposit of carbonate of lime, that the Moas’ bones are found. Dr. Thomson got only four skulls in this cave, and the scarcity of them was accounted for by their use in former days as powder-holders. There was nothing to lead him to think that these bones had been deposited in the cave by water, for he found a remnant of almost every bone in the body, from the spine and the rings of the trachea down to the last bone of the toes. The bones belonged to the largest and also to the smaller species of Moas. It would require several days’ labour of many men to clear out the bottom of this cave properly, in order to see what bones it contains; but, as far as Dr. Thomson saw, there were no osseous remains of man or of any animals, except Moas, in it, nor any marks of fire, sculpture, nor figures of any kind on the walls of the cave. There are, no doubt, many other grottoes and cavities containing Moas’ bones in the islands, but they are carefully kept secret by the natives, as, on account of the high price paid for the bones, they may almost be regarded as small gold-mines. CHAPTER XX. SUBTERRANEAN RELICS OF PREHISTORIC MAN. The Peat Mosses of Denmark—Shell Mounds—Swiss Lacustrine Dwellings— Ancient Mounds in the Valley of the Mississippi—The Caves in the Valley of the Meuse—Dr. Schmerling—Human Skulls in the Cave of Engis— Explorations of Sir Charles Lyell in the Cave of Engihoul—Caverns of Brixham—Caves of Gower—the Sepulchral Grotto of Aurignac—Flint Implements discovered in the Valley of the Somme—Gray’s Inn Lane an ancient Hunting Ground for Mammoths.