The _débris_ in the small bore-hole contains pieces of a maximum size of about 8 cubic inches. In the large boring, pieces of rock measuring 32 cubic inches have been found. As a rule, however, the material is beaten very fine, having much the appearance of mud or sand. In both the large and the small borings the _débris_ is raised by a shell, similar to Figs. 105, 106, and in this system consisting of a wrought-iron cylinder, 3 feet 3 inches in diameter by 6 feet 9 inches long, and containing two flap-valves at the bottom, through which the excavated material enters. This apparatus is passed down the shaft by the bore-rods, and it is moved up and down through a distance varying from 6 to 8 inches, for about a quarter of an hour, and is then drawn up and emptied. In some cases where the rock is hard, three sizes of trepan are used consecutively, the sizes being 5 feet, 8 feet, and 13 feet. The several other tools and appliances used during the boring operations are shown, Figs. 135 to 140, including the key, Figs. 139, 140, used at the surface to disconnect the rods, the hook on which each rod is hung after being raised to the high platform and there detached, the bar upon which the hooks are moved, and the fork for suspending the rods or tools from the rollers when it is desired to move the rods or tools from above the shaft. [Illustration: Connections to the Trepan and Spears or Rods. Figs. 143-146.] Figs. 141 to 146 are of the connections to the trepan and spears or rods. Should broken tools fall into the shaft, several varieties of apparatus are used for their recovery. In case of broken rods of any kind having a protuberance that can be clutched, a hook or crow, Figs. 137, 138, of an epicycloidal form, enables the object to be taken hold of very readily. Where the broken part has no shoulder which can be held, but is simply a bar, the apparatus shown by Figs. 147, 148, is employed. This is composed of two parts. The rods, the bottom of which have teeth inside, are prevented from diverging by the cone and slide on the main rods. When passed over a rod or pipe, they clutch it by means of the teeth, and draw it up. Chaudron has, by this tool, raised a column of pipes 295 feet in length and 8 inches in diameter. An instrument, called a "grapin," Figs. 149, 150, is used for raising broken teeth or other small objects which may have fallen into the bottom of the shaft. This tool also has one part sliding in the other, and is lowered with the claws closed. The parts are moved by two ropes worked from the surface. By weighting the cross-bar, which is attached to the moving parts, the pressure desired can be exerted on the claws. The weight is then lifted, the claws are opened, and are made to close upon the substance to be raised. This instrument is now seldom required. [Illustration: Pipe or Rod Recovery Tool. Figs. 147, 148.] [Illustration: Grapin. Figs. 149, 150.]