9. In the exploration of water-caves, in which there are sometimes sheets of water of considerable size and depth, a raft may be used, such as that devised by Mr. James Parker for the navigation of the great cave of Wookey Hole. It consisted of a platform supported on barrels and built as follows: A frame of stout poles was made; two, a a, being eight feet long, with four others, b, c, lashed firmly across, each four feet in length. The space d was converted into a platform by nailing boards across, and this was buoyed up by a beer-barrel at each end in the interspace e. The barrels were attached to the raft by two loops of rope g, passing over from b to c, and thus kept in place, although they freely twisted and turned in actual use. The ropes had an advantage over iron hoops for the attachment of the barrels, because when they were tightened the platform was raised above the water, when they were loosened it was lowered, and thus the raft could be adjusted to the weight to be carried, to the depth of the water, and the distance of the water-line from the roof. A raft of this kind will bear three persons, and is sufficiently light to be carried over the shallows. With it Mr. Parker made his way for a considerable distance in the Wookey Hole cavern, and subsequently I penetrated as far as the water-line would allow me to get. A long pole is also necessary for punting. Mr. Parker found by experience that a raft made of boards nailed on the top of two beer-barrels was too unstable to be of any use. In making his way across subterranean pools the cave-hunter ought to be prepared for accidents, for the depth is very uncertain, and the water sufficiently cold to cause cramp. For the exploration of ordinary water-caves a 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.

The Victoria Cave, where the demarcation between the strata was very distinct, was explored, while the work was under my direction up to September 1873, in a somewhat similar fashion. It was, however, impossible on account of the great depth of the deposits to cut a passage down to the rock at the entrance. We therefore examined the superficial strata throughout the cave, merely gauging the thickness of those below by sinking three shafts. Where a cave is sufficiently high to allow of the work being carried on, it is better to clear out one stratum before another is disturbed.

The most elaborate and perfect method of cave exploration is that which has been used by the committee in Kent’s Hole, under the superintendence of Mr. Pengelly, who writes as follows:274—

“The following is the method of exploration which has been observed from the commencement, and which it is believed affords a simple and correct method of determining the exact position of every object which has been found.

“1. The black soil accessible between the masses of limestone on the surface was carefully examined and removed.

“2. The limestone blocks occupying the surface of the deposits were blasted and otherwise broken up, and taken out of the cavern.

“3. A line termed the ‘datum-line,’ is stretched horizontally from a fixed point at the entrance to another at the back of the chamber.

“4. Lines, one foot apart, are drawn at right angles to the datum-line, and therefore parallel to one another, across the chamber so as to divide the surface of the deposit into belts termed ‘parallels.’

“5. In each parallel the black mould which the limestone masses had covered is first examined and removed, and then the stalagmite breccia, so as to lay bare the surface of the cave-earth.

“6. Horizontal lines, a foot apart, are then drawn from side to side across the vertical face of the section so as to divide the parallel into four layers or ‘levels,’ each a foot deep.

“Finally each level is divided into lengths called ‘yards,’ each three feet long, and measured right and left from the datum-line as an axis of abscissÆ.

“In fine, the cave-earth is excavated in vertical slices or parallels four feet high, one foot thick, and as long as the chamber is broad, where this breadth does not exceed thirty feet. Each parallel is taken out in levels one foot high, and in each level in horizontal prisms three feet long and a foot square in the section, so that each contains three cubic feet of material.

“This material, after being carefully examined in situ by candlelight, is taken to the door and re-examined by daylight, after which it is at once removed without the cavern. A box is appropriated to each yard exclusively, and in it are placed all the objects of interest which the prism yields. The boxes, each having a label containing the data necessary for defining the situation of its contents, are daily sent to the honorary secretary of the committee, by whom the specimens are at once cleaned and packed in fresh boxes. The labels are numbered and packed with the specimens to which they respectively belong, and a record of the day’s work is entered in a diary.

“The same method is followed in the examination of the black mould, and also of the stalagmitic breccia, with the single exception that in these cases the parallels are not divided into levels and yards.”

A careful record of the work, and minute sections should be taken daily on the spot.

The Stalagmitic Floor to be broken up.

In all cases the crystalline flooring of stalagmite and stalagmitic breccias which often occur, should be broken up, or, if necessary, blasted with gunpowder. The former very frequently conceals the pleistocene remains, and the latter, which is in Kent’s Hole many feet thick, often contains the traces of man and wild animals. Sometimes it is very difficult to distinguish the breccia from the rocky floor.

Where the ossiferous deposit fills a vertical fissure it must be worked on the same plan as in ochre-mining, by sinking a shaft. To dig into it from below (where this is possible) is very dangerous, because of the large imbedded stones which fall sometimes without any warning.

The Preservation of Fossil Remains.

The fossil bones and teeth, which have very generally lost their gelatine and have a tendency to crumble and split to pieces in drying, should be gradually dried, and from time to time saturated with a weak hot solution of gelatine or glue. Silicate of soda, sometimes called “liquid glass,” or melted paraffin (not the oil), may also be used for the same purpose. If the bones are extremely soft, they may be rescued from destruction by letting them dry in the matrix, saturating them and the matrix with a solution of gelatine, and then clearing off the latter. In this manner I preserved the skull of the musk sheep which is now in the Museum of the Geological Survey in Jermyn Street, London.