170

QUARRY.

Through the copper pipe at d a small leaden pipe is introduced, about half an inchin diameter, formed with a funnel f at the top, and is passed down to within about1 inch from the bottom; the upper orifice of the copper tube round the leaden oneat g being filled with a packing of hemp. Matters being thus adjusted, dilutenitric acid is poured through the funnel and leaden pipe, which, dissolving thecalcareous rock at the bottom, causes an effervescence, and a substance containingthe dissolved lime is forced out from the orifice c, the process being continueduntil, from the quantity of acid consumed, it is judged that the chamber is sufficientlyenlarged. Other acids, such as muriatic or sulphuric, will produce the same effect,but the result of the chemical solution will depend on the nature of the stone and theproportion of its chemical constituents.

It may be assumed that I lb. of powder, when loosely poured, but not shaken orcompressed, will occupy about 30 cubic inches; or 1 cubic foot will weigh about57 2 tts.; consequently a hole 1 inch in diameter and 1 inch in depth will weigh•419 of an ounce, multiplying which by the square of the diameter of the hole ininches, will give the weight of an inch in depth of powder in any given hole; whencecan readily be determined either the length of hole for a given charge, or the chargein a given space.

Gunpowder varies very materially in quality, a comparison between Merchants’blasting powder and Government cannon powder giving arcs by an eprouvette gunfrom 12'0 to 21'0 degrees: it is therefore of very great importance that powdershould be tried before purchasing or commencing to use it in quarrying, so as toprevent disappointment in the expected results, or an excessive use of pow'der.

The benefits resulting from the use of strong powder are evident:

1st. Smaller quantities are required, and consequently less stowage room.

2ndly. Greater effect is produced in comparison to the labour expended in boring.

3rdly. Increased resistance in the tamping, th6 powder occupying less space, andleaving more for the tamping.

In determining the most economic method of producing a given quantity of stonefrom a quarry of any particular description of rock, the following points are first tobe ascertained:

1. The constant from which the charge is to be calculated.

2. The speed with which holes of different bores can be driven.

3. The effect of.agents, such as small charges or acids, in enlarging chambers.

4. The face which can he established in the quarry; for it is obvious that thehigher this face is, if the charge is placed behind it, the greater will be the propor-tional effect on the mass dislodged; the powder acting on a like mass in eitherinstance, hut leaving a much greater mass to be dislodged by its own weight in theone than in the other.

These data having been determined, and the size of the block required beingknown, the calculation is to be made whether large charges are to be adopted or asuccession of smaller ones.

Large charges have one decided advantage, not requiring that the quarry shouldbe so often cleared of workmen during firing.

The loading of mines in rock requires great care, to prevent accidents, the safetywith which the operation is performed in a great measure depending on it. A fewgrains of powder loose on the side of the bore-hole may produce explosion intamping. For the purpose of loading, the use of copper vessels is recommended.

A copper canister, with cover, to contain the powder;

A set of copper measures containing given weights of powder (1 lb., 4 oz., and1 oz.);