and other tools. One of the best descriptions is the Golden Green Wattle (Acacia decurrens, var. mollis). Wedge. When the ground, though harder, is nevertheless "jointy," or traversed by many natural fissures, the wedge comes into play. The Cornish tool known as a gad is a pointed wedge (Fig. 155). The so-called "pick and gad" work conFIG. 155. sists in breaking away the easy ground with the point of the pick, wedging off pieces with the gad, driven in by a sledge or the poll of the pick, or prising them off with the pick after they have been loosened by the gad. The Saxon gad is held on a little handle, and is struck with a hammer. It is used like the Cornish gad for wedging off pieces of jointy ground, and in former days even hard rocks were excavated by its aid. The process consisted in chipping out a series of parallel grooves, and then chipping away the ridges left between them. As a method of driving levels or sinking shafts, this process is naturally obsolete; but it is useful on a small scale for cutting recesses (hitches) for fixing timber, for dressing the sides of levels or shafts before putting in dams, and for doing work in places where blasting might injure pumps or other machinery. Saws.-Freestone is sometimes excavated by sawing. The saws are 6 or 8 feet long, and I foot wide. The wooden handle FIG. 156. can be fixed so that no part projects above the saw when the tool is used close to the roof (Fig. 156). Tools used for Boring and Blasting.-We now come to hard ground; and in this class we have a large propor tion of the rocks met with by the miner, such as slate of various kinds, hard grit and sandstone, limestor.e, the metamorphic schists, granite, and the contents of many mineral veins. Rocks of this kind are attacked by boring and blasting. The tools employed are the auger, jumper, or borer (drill), hammer or sledge (mallet, Cornwall), scraper and charger, tamping bar or stemmer, pricker or needle, claying bar and crowbar. Augers. At English gypsum mines a tool resembling the carpenter's shell-auger is regularly used for boring holes for blasting. It is worked by a cross handle, and makes a hole 1 inch in diameter. Boring is done in the bituminous limestone of Seyssel by screw-augers in a similar manner. Elliott Drill.-Screw-augers mounted upon stands are common. Fig. 157 represents the Elliott drill, which consists of an auger inserted into a socket upon a feed-screw c, which works upon a worm-wheel a, held fast in a ring, when the screw clamp b is tightened. On moving a ratchet brace backwards and forwards, c is turned round, carrying the auger with it, and when the wormwheel is tight, it advances slowly at the same time. If a very hard piece of rock prevents the penetration of the auger, the worm-wheel slips in the ring, and, by suitably arranging the tightness of the clamp b, the machine can be made to accommodate its advance to the nature of the rock. The drill itself is made of a bar of twisted steel, which clears itself of the débris to a certain extent; when it has penetrated as far as it will go, the clamp is loosened, enabling the feedscrew to be drawn back rapidly without rotating at all. A longer drill is put in, and work continued. The light frame or standard is made in two halves, and by shifting a pin its length can be altered to suit the height of the FIG. 158. FIG. 157. working place, whilst the final tightening is done by a screw at the bottom. Ratchet Drill.-Where even more simplicity is required, a selffeeding ratchet drill can be employed, with a piece of timber set up in the working place as an abutment. An auger is inserted into a socket upon a feed-screw a (Fig. 158), working in the nut b, attached to a long sheath. When the ratchet handle c is worked, a revolves and at the same time advances from the feed-nut, carrying the auger with it. The sheath is prevented from turning by putting the eye of a pin over one of the projecting pegs at the rear end, and allowing the pin to be brought up by the first twists against the piece of timber. For enabling the feed-screw, after it has advanced to its full length, to be quickly returned into the sheath, the Hardy Patent Pick Company sometimes use Stayner's Patent Split Nut, instead of an ordinary nut; when the split nut is loosened, the feed-screw can be moved back without loss of time in turning. These augers worked by hand will do good work in moderately hard ground, such as tough shale, slate, and even sandstone. Jumper. The simplest tool for boring holes by percussive action is the jumper, a bar of iron tipped with steel, forged into a chisel-shaped edge. It is struck against the rock, and turned a little at each blow, and in this way chips out a cylindrical hole. Fig. 159 represents the jumper used in the lead bearing sandstone at Mechernich, made of a bar of iron inch in diameter, and 7 to 10 feet in length. As the rock is soft, the cutting edge can be made wide and sharp. The exact angle of the actual cutting edge of a jumper which I measured was 42°; the final sharpening is done with a file. At the open workings for ironstone in Northamptonshire, the edge comes to a point in the middle (Fig. 160). The jumper used in the Festiniog slate mines (Fig. 161) has a swelling in the middle, and both ends are sharpened; the short end serves for beginning a hole, the large one for completing it. The ordinary sharpening is done by heating the end red-hot, and filing it to the desired form while the jumper is held in a vice. It is allowed to cool gradually, and then is heated again in the forge, hardened in water and tempered. The jumper for boring holes at any angle in the rock-salt of Cheshire has a swelling in the middle, and tapers gradually to each end. The jumper of the Cleveland ironstone miner (Fig. 162) has the swelling at one end, and will bore holes at any angle. Like the Festiniog tool, it is sharpened by being hammered into shape, and finally filed when hot. Borers. When the rocks are harder, and also in situations where a jumper cannot be wielded, the miner must have recourse to the borer or drill, which is simply a steel chisel (Fig. 163). The steel is brought to the mine in the form of round or octagonal bars, and is cut up by the mine smith into pieces of the required length; one end is forged into a chisel-shaped edge, the exact shape and degree of sharpness varying according to the hardness of the rock. For hand-drilling the steel is usually inch to 1 inch in diameter, but inch or even inch steel is sometimes used. The old plan of making the drill of iron, and welding on a piece of steel for the cutting edge (bit), is almost extinct in this country. The shape of the bit of the hand drills used at Minera mine, North Wales, is shown in Figs. 164 and 165, the angle of the edge being 84° The drills used with the compressed air machines at Minera are rather blunter than a right angle. At a limestone quarry, near the mine, the drills have two cutting edges arranged in step-fashion. Drills for hard rocks are sharpened entirely at the forge; the cutting edge is hammered into the desired shape on the anvil FIGS. 164 & 165. -158 INS. In while red-hot, and then hardened to suit the particular requirements of the user. many cases the desired temper is obtained by plunging the tool when at a blood-colour into cold water, and allowing it to remain there; but for soft rock the tool will work efficiently after the hardness has been reduced by annealing. In the case of slate the smith heats the end of the jumper to blood-colour, and just dips the edge into water for a few seconds. He now watches its colour as it cools down, and stops the annealing or tempering action by plunging the tool into cold water when a certain shade of blue has been reached. Some smiths rub the edge of the tool upon a piece of board with a little sand, in order to be able to follow the changes of hue with precision. Before the introduction of machines, as many as fifty drills were sometimes blunted in boring a hole 2 feet deep by hand at an iron pyrites mine in Carnarvonshire. This is an exceptional case, but nevertheless the importance of having a good smith at a mine where much sharpening has to be done cannot be overestimated. A tool called a "bull" is employed in boring holes in tough hæmatite and tough clay in some districts. It is a bar pointed at one end and provided with an eye at the other. It is driven into the ore with a sledge, and by putting another bar through the eye it can be withdrawn without difficulty. There is practically no difference between it and the claying bar (Fig. 172). Hammers.—The hole is bored by striking the drill with a hammer or sledge, and turning it after each blow. Boring is said to be single-handed if the miner holds the drill in one hand and wields the hammer with the other; whilst it is called doublehanded when one man strikes and another turns. Sometimes there are two men to strike, one after the other, whilst a third man turns the drill. In starting a hole a short drill is chosen, and longer ones are taken as the hole is deepened; the smith is careful to make the cutting edges (bits) diminish slightly in width as the borers increase in length, because the hole gradually decreases in diameter as the tool wears. The bore-hole is therefore not a true |