The set of boring-rods consists of one chisel yard long, rod yard, rod 1 yard, rod 2 yards; the remaining rods are of lengths which under the particular circumstances are most convenient, say 2 yards, 3 yards, 4 yards, 6 yards, or even more. The rod must not be longer than can be conveniently transported, handled, and suspended from the frame with the lower end above the bore-hole. Four yards is often a convenient length; they are, however, often made in 2-yard lengths; these can be screwed up into 4-yard or 6-yard lengths as required. A loose socket-joint is shown in Fig. 75 (25).

The process of boring is as follows: If the hole is probably to be a shallow one-from 3 to 15 yards-the bore-hole is begun with the chisel screwed on to the shorter rods without any preliminary work, simply putting on the ground a piece of plank with a hole in it, through which the chisel is passed; the boring is made by two or three men. Rods are added as the hole gets deeper, up to a depth of 15 yards; below that depth four or five men are required, and also a windlass and pulley frame, as shown in Fig. 75 (18, 19, 22). After 30 yards a spring-pole or other contrivance is necessary to sustain the weight of the rods. Fig. 75a shows also a method of boring by lever instead of spring-pole, and also a windlass and frame. These frames are now often made of iron tubes or bars. If the hole is probably to be from 20 to 50 yards, it is started more carefully. It is a common practice to dig a pit 6 or 7 feet in diameter and about 7 feet deep. The digging of this pit serves several purposes. In the first place, it can be done as quickly and cheaply as an equal length of boring at a depth of over 25 yards. In the second place, it clears away the loose ground at the surface, which might interfere with the boring. In the third place, it has the effect of additional height on the pulleyframe, just making a short pulley-frame available for drawing the rods in lengths of 4 to 6 yards. In the fourth place, the pit shelters the men from storms.

At the bottom of the pit a smaller hole is hacked up with pick-axe and drill, into which an iron pipe can be placed (Fig. 75, 22). This pipe may be from 2 to 6 feet in length (according to the probable depth and importance of the hole); the bore of the pipe, say 4 inches, is just sufficient to take the largest chisel that may be used. The pipe has a flange at the top end. It is placed vertically in the hole in the centre of the pit, and the earth is firmly rammed round it; the flange rests either on the ground or on a plank with a hole in it, through which the pipe is passed. The pipe now forms a permanent entrance to the hole and a vertical guide for the chisel.

Above the pit is fixed the spring-pole (Fig. 75, 17). This is a

young larch tree about 30 feet in length. The butt end is placed between two stout posts, which are securely planted in the ground; an iron pin about 1 inch in diameter passes through the posts and the pole, and so holds the pole down. At a distance, that may be varied from time to time, of say from 3 up to 8 feet from the butt end, a block of wood is placed under the pole so as to raise the end of it that is over the bore-hole to a convenient height-say 10 or 12 feet. There is also a pulley-frame. For shallow borings the frame consists of three legs lashed together (or pinned) at the top, from which a pulley (“snatch-block") is suspended. A windlass with a good hemp rope is also placed on one side and weighted down with stones. Fig. 75a shows a pulley frame, windlass, and balance-weight lever, sometimes used instead of a spring-pole.

The boring is now begun. A couple of men take the chisel screwed on to the end of a rod, and, putting it through the pipe, strike it on the ground, turning it round between each blow; they also put some water in the hole to facilitate the cutting. When they have bored the hole about a half-yard they put on the crosshead, by means of which they can more easily lift and turn the rods; after boring another half-yard, they draw the rods, take off the short rods, and substitute a 6-foot rod, which with the chisel and cross-head make up a length of three yards; when the boring is another half-yard deeper, the half-yard rod is added at the top under the cross-head; after another half-yard is bored, the yard length is substituted for the half-yard length, and so on, the additions being so arranged as always to keep the cross-head

The depth

As soon as

at the most convenient height for the men to handle. of the hole is always known by the length of rods. the length of rods gets too great for three or four men to lift with ease, the cross-head is suspended by a chain and swivelhook from the end of the spring-pole. The weight of the rods bends the pole down; the chain is adjusted so that the pole holds the rods suspended just clear of the bottom of the hole. The men now press the chisel down to the bottom, and then lift it up assisted by the pole; then, pressing it down again, they strike a smart blow with the chisel, turning the cross-head between each blow, so that with every eight blows they make the chisel turn completely round.

After working for some time, varying from ten minutes to an hour, the bottom of the hole becomes choked with dirt or the chisel gets blunt; the rods are then drawn. This is done by means of the winch with a rope over the pulley. There is a clawhook (Fig. 75, 20) at the end of the rope, which takes hold of the shoulder in the rod next below the cross-head piece. By this the rods are lifted, then unhooked from the spring-pole, and lowered an inch or two on to a fork (Fig. 75, 13) placed over the hole, which supports the rods by the lower shoulder. Then the crosshead is unscrewed by the key (Fig. 75, 14) and removed; the rods are now lifted as high as convenient, and again placed on the fork; the upper rods are unscrewed and reared up on one side of the pit or the pulley-frame. This operation is repeated until all the rods are drawn.

When the chisel is drawn it must be carefully examined, because adhering to it will be the débris from the bottom of the hole, which will show the nature of the stratum in which the chisel is working. When some small bits of this earth have been found and examined, it will be at once apparent whether the stratum is sandy or clayey, light or dark, coal or stone; whether it is hard or soft has been already ascertained by the men who were boring feeling the effect of each blow. Specimens of the stuff are to be carefully preserved and labelled.

The sludger (sometimes called the cleanser or sand-pump) (Fig. 75, 4) is now screwed on to the rods and lowered down the hole. The lengths of rod have now to be screwed together again as in turn they are put into the hole, until the sludger rests upon the bottom. The sludger is often auger-ended, and in that case it is turned round so as to screw into the sludge; it is also lifted up and down so as to force the semi-liquid sludge up through the valve in the bottom. The rods are then drawn again in the same way as when drawing the chisel. When the sludger reaches the top it is carried very carefully to a trough, into which

the liquid contents are poured, the water being allowed to run off, and the sludge carefully examined, and some of the solid portions picked out, and specimens of the semi-solid parts put on one side to dry. The examination of the contents of the sludger is the most critical and important part of the operation, as by it mainly the nature of the ground can be told; and, the greater portion being in the form of sludge, the description of the ground has to be inferred, as it is obviously not identical with the pulverized material extracted. If the sludge is composed of sand, and if when boring the ground was found to be hard, it is evident that the stratum bored through was sandstone; if the sludge is clayey, and the boring was hard, it is evident that the stratum was a hard shale or a hard bind; if sand and clay are mixed in the sludge, the stratum is then a sandy bind or a sandy shale. The colour of the rock will be similar to the colour of the sludge, but there will also be fragments of the ground which will indicate its nature. The thickness of each stratum can generally be ascertained accurately, because, when the chisel passes from one stratum to another, some difference is felt by the man at the cross-head, and the depth of rods in the hole is then exactly noted. If the ground is not very hard the sludger will have to be sent down twice before the hole is clean. Then the chisel is sent down again; a sharp one is sent down each time.

It is often necessary to obtain larger specimens of the ground through which a boring is made than the small bits that adhere to the chisel or are drawn by the sludger, and for this purpose a core-cutter is used. This cutter often consists of a four-pronged fork. At the end of each prong is a chisel, as shown in Fig. 75 (15). This fork, instead of cutting the whole of the ground away, only cuts a ring, leaving a core standing up in the middle. A different kind of core-cutter, as shown in Fig. 75 (24), is sometimes used; this has more of a grinding action, and by twisting it round a circular groove is made. The core having been cut, the next process is to break it off and lift it up, using the coreextractor, as shown in Fig. 75 (16). The bell a is lowered over the core d; the wedge b jams one side of the bell against the core, thus breaking it off; the springs help to hold the core in the bell whilst it is being drawn up. Another coreextractor is shown in Fig. 76. The cylinder a a is lowered

2800

CORE

FIG. 76.-Coregrapnel.

down over the core, the small steel-spring cutters b being forced back by the entering core; the cylinder is now turned round and slightly lowered and lifted alternately so as to cause the points of the four steel cutters to enter into the lower part of the core c. The iron ring d is lowered down inside the cylinder a, and over the core and on to the top of the four steel cutters, forcing them against the core. The cylinder a is now jerked upwards, and the core broken off and drawn to the top. In order to get a good core by this process it is necessary that the hole should not be too small, and it would probably be of little use trying to get a core with these tools in a hole much less than 4 inches in diameter. When a core can be got, it gives much more satisfactory evidence of the nature of the strata than can be obtained with the sludger.

Details of Apparatus for recording Direction and Angle of Dip.-In some cases the direction and the amount of dip of the strata can be ascertained from the core. Suppose, for instance, that when the core reaches the top of the hole it has not been turned since it was detached from the solid ground, then, if there are any lines of bedding in the sample, they may be noted, both as to direction and angle. But to avoid any error resulting from the turning of the core during extraction, it is sometimes marked before it is detached from the solid ground. A boringtool, the lower end of which is a ring on which is fastened a cutter at the outer edge, is lowered into the hole. This cutter is very gently struck upon the top of the core, the position of the cutter as regards points of the compass being noted at the time the blows are struck. When the core is subsequently withdrawn, the marked side is placed in the same direction as that in which the cutter was previously held.

Speed of Borings. When a hole is first started, with good men and good tackle, a boring in the coal measures, shale and bind, may be made at the rate of 12 inches an hour; but after a depth of some 20 yards is reached, the speed is much reduced, owing to the time required for drawing and lowering the rods. It is evident that the time thus occupied will increase with the depth of the hole, so that in deep bore-holes the progress is very slow, no matter how easy to bore may be the stratum, and with such apparatus as has been described the speed of boring would be quickly reduced to 12 inches in 24 hours.

Machine-Boring.-In order to increase the speed of boring, steam machinery is employed and other methods adopted to save time. If a high pulley-frame is used, a long length of rods can be unscrewed at once; thus if the pulley is about 70 feet above the platform, 60 feet of rods can be detached at once,