raft is unnecessary, but no attempt should be made without a rope. In Yorkshire and Derbyshire there is an unlimited field for adventure in the subterranean water-courses. 10. The most convenient lights for use in caves are the common composite candles. Paraffin candles are open to the objection that they gutter, lanthorns do not give a sufficiently diffused light, and the smoke of paraffin torches, or flambeaux dipped in turpentine or tar is intolerable. Magnesium wire reveals the beauties of the higher roofs. _The Search after Ossiferous Caves._ Many of the ossiferous caves, and especially those of the neolithic and pleistocene ages, have their entrances masked by débris which has been accumulated from the surface above during the long lapse of ages. In their discovery I have found rabbits, foxes, and badgers of the greatest service, since these animals generally make their burrows in such places. And where their earths are met with at the base of a vertical wall of rock, I have very generally found a cave. They were my sole guides to the discovery of the five sepulchral caves at Perthi Chwareu, described in the fifth chapter, in a district in which up to that time caves were not known to exist. The dwellers in caves very generally chose for their habitations the sunny side of the ravines and valleys, and the spots which commanded a wide view, and, therefore, their remains are to be looked for in those places, rather than on the cold and sunless sides, or where an enemy might approach without observation. _The Scientific Methods of Cave-digging._ The exploration of an ossiferous cavern with sufficient accuracy to be of scientific value, may be carried out in all tunnel caves, or those extending horizontally into the rock, by one of the three following methods which may be adapted to the local conditions:-- The first step to take in all cases is to make a plan of the entrance, and to cut a passage down to the rock at the entrance, so as to obtain a clear idea of the sequence of the strata. In the hyæna-den at Wookey Hole, we first of all cut a passage through the cave-earth which extended from the roof to the floor, and then removed the earth on either side in blocks, until ultimately the chamber and passages described in the eighth chapter were cleared of their contents. Our work was measured every evening, and each bone and object found was labelled with the date which was recorded on the ground plan. Vertical sections were also taken from time to time. This mode, supplemented by constant supervision of the workmen, was sufficiently accurate to satisfy the demands of scientific research.