Of course, there are many methods of shaft sinking which depend greatly on the situation of the property. In places it is preferable to sink along the dip of the reef, and in others vertical shafts are sunk through a great amount of dead rock to meet the reef.

Hauling and pumping machinery, compressed air, and machine drills are used when sinking at greater depths. Otherwise, in the starting and working of smaller concerns, the primitive way of bringing the ore and water in buckets to the surface by means of a windlass, and, later on, small machinery, is adopted.

If the reef crops out on a steep mountain, and dips with the slope of the same, or is exposed on the face of the mountain, the cheapest way will be to drive to meet it, or along the strike (Fig. 14).

For any further deep mining, hauling and pumping will be necessary, in which, of course, different methods from those of general prospecting are adopted.

7. Timbering.-In the event of any prospectings becoming dangerous, through cracks, decomposition, boulders, or water, timbering is necessary. This, of course, depends on the extent

HAA

Fig. 15.-Wedged timber.
a, Timber; b, loose rock.

α

b

Fig. 16.-Sets of timber.

of the danger. In solitary places, where a piece of rock hangs loose, by which the other rocks are not affected, a simple means of support is a piece of timber wedged firmly against it (Fig. 15). In places where a drive or shaft is very shaky, a complete set of timbering must be made, which can be fitted, screwed, or wedged together (Fig. 16).

Behind two sets of timber long poles should be horizontally fixed above, and placed on both sides of the tunnel or drive, so that the space between the timber and the tunnel wall can be firmly packed with debris. This prevents little stones from falling out from time to time, making room for large heavy slips,

which would in many cases break the frame work (Fig. 17). In the same way shafts may be timbered, and the sets only logged, as in Fig. 18, but great care should be taken to wedge the sides very firmly, so that nothing can fall on men working below.

In making shafts during prospecting, windlasses and buckets are needed to bring the material to the surface. The framework should be 4 feet by 6 feet, and be made of timber well fitted together (Fig. 19).

H

a

Fig. 19.

-a and c show the manner of preparing; b, framework of windlasses.

The drum should be cut in half, lengthways, an iron bar fitted in the middle, and the two parts well screwed together as in Fig. 19, c.

The rope should be well fastened with nails at one end, or serious accidents may happen by the bucket dropping down when the work is proceeding.

8. Blasting and Drilling.-Experience in blasting and drilling is most important, as the amount of work done depends very much on this. The steel drills should be made round, not too pointed, but sharp (Fig. 20), and hardened according to the nature of the rock. The hole which is to be made should be

placed at a spot where no fractures can be seen, as the explosives are not effective in broken rock owing to small pieces being blown out, without moving the bulk of the rock. The drill should be held steadily at the chosen place, and, at every blow of the hammer, rotated, so that the hole keeps perfectly circular, and the jamming of drills is avoided. If the hole is kept constantly wet by pouring in water, the work proceeds much more quickly. The mud accumulated during boring is removed by a thin piece of iron, with a small disc at one end, called a scraper; on valuable ground it is advisable to test this mud for its contents.

After the hole is finished the dynamite necessary (usually one or two cartridges) is tightly rammed to the bottom by a wooden stick; there is danger in using an iron rod.

Fig. 20.-Drill sharpened.

The detonator, in which the fuse has already been fixed, is carefully pushed into a half cartridge of dynamite. The whole is then placed gently on the top of the other cartridges already in the hole, which is then filled up tightly with fine soil, pressed in with a wooden stick.

To more readily apply light at the end of the fuse, a small slit is made and a little dynamite placed in it. One should be thoroughly acquainted with the length of the fuse required, so as to gain sufficient time to retreat to a safe place before the explosion. In wet places the contiguous ends of the detonator and fuse should be greased in order to prevent water from getting in between them, and the holes filled with water tamping.

In the case of an unexploded charge, which is mostly caused by a bad fuse not burning to the end, one should in no case visit the place again under thirty minutes; it is therefore wise to blast during the meal hours. It is important to count the number of charges, when exploding.

The best way with unexploded charges would be either to remove the tamping carefully and place a new charge on the top of it, or to drill another hole close by, but taking care not to bore into the former. Accidents arise chiefly through carelessness.

It is also important to know how to place the drill holes, so that the explosives may exercise their utmost power.