103

C—3.

6. Ventilate the sketch section of mine-workings (not here shown), show by arrows the direction of the air-current round all the miners, and by dotted lines the position of any air-boxes, sollars, or brattice necessary; and state how the natural ventilation may be improved without having recourse to machinery, water, steam, or furnace. Subject D. — Tapping Water in Mines, and Mode of constructing Dams in Underground Workings to keep the Water back. 1. In sinking a shaft through solid rock, at 50 ft. in depth a fissure is encountered which produces a considerable flow of water; the shaft is to be sunk to a depth of 1,000 ft.: what steps would you take to prevent the flow of water getting down the shaft as the sinking proceeded? Give full details of the measures you would adopt. 2. A crosscut in hard rock is to be utilised as a dam ; the crosscut is 7 ft. by 6 ft.; the water is to rise to a height of 4 ft.: describe fully the material you would use, and your mode of construction. 3. A breastwork is to be constructed in a similar crosscut to the above, where the water is to rise to a height of 300 ft. above the centre of the breastwork : give the total pressure on the structure ; also (a) your mode of construction, (b) the material you would use, and your reasons. 4. A winze (securely timbered with black-birch) has been sunk on the lode to a depth of 70 ft., and is then allowed to fill with water ; after twelve months an uprise to connect with the bottom of the winze is within 20 ft. of the holing through ; the survey can be relied on : what precautions (if any) would you now take to insure the safety of the workmen when making the connection ? Subject E.— Blasting, and the Use of Explosives. 1. A borehole 2 in. in diameter is filled with blasting-gelatine to a depth of 6 in.: required the weight of the charge. 2. In a similar borehole to the above, what weight of gelignite would be required to do the same work? 3. What explosives would you use for the following works: (a) Sinking a wet shaft; (b) driving a level through very hard rock ; (c) stoping on medium-hard quartz? Give your reasons in each case. 4. Give the weight and composition of charge of a No. 6 detonator (Thistle brand), (a) for safety fuse, (b) for electric blasting. 5. In case of a misfire, what time would you allow to elapse before returning to the face ? 6. What is the most powerful blasting-explosive known ? and give its composition. 7. What do you consider the best fuse for blasting in water or very wet ground? 8. A hole is to be charged with gelignite ; the temperature is 40° Fahr. : describe fully what steps (if any) you would take before charging the hole; also state the six operations required in charging the hole. 9. To fire a group of holes simultaneously by electricity, give sketches showing how you connect the wires in series and in parallel, and state what fuses you would use in each case ; also state what test you would apply to make certain that there was no break in the circuit. 10. A missed shot in electric blasting may occur from either one of four causes : name them. Subject F.— A Knowledge of Arithmetic and the Method of Keeping Mining Accounts. 1. Evaluate and A/-000125. - 169 T 2. A bar of gold as produced from a mine contained 302-67 oz., which after melting at the mint was worth 320-10 oz. of standard gold. What is the value per ounce of the gold as produced from the mine, the mint value of standard gold being £3 17s. 10id. sterling per ounce ? 3. An analysis of expenditure at a large quartz mine is subdivided under the following headings : (a) Mining; (6) Treatment; (c) Realisation of Bullion ; (d) General Expenses ; (c) Total Working Expenses; (/) Development; (g) Capital Account; (h) Total. Specify the principal items which should appear under the above headings. Subject H. — Pumping Appliances and the Drainage of Mines. 1. What quantity of coal per indicated horse-power per hour would be consumed under favourable circumstances by a pumping-engine ? 2. Is electric driving suitable for single- or double-acting plunger or bucket pumps ? State the reasons for your answer. 3. What do you consider the practical limit to the length of a draw-lift section of pumps ? State the disadvantages of exceeding such a limit.