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3. A fan 26ft. in diameter by Bft. 6in. wide revolves sixty times per minute with a coefficient discharge of 45, what is the discharge per minute ? 4. In what cases can you apply the water-gauge in a mine, and why is it not more generally used? 5. A furnace 'circulates 80,000 cubic feet of air per minute with an upcast 280 fathoms deep, what amount of air would it circulate with the same conditions but an upcast only 100 fathoms deep? 6. In a shallow mine free from gas compare the furnace and fan, and give your opinion at what epth the relative efficiency is reversed ?

IV. — On the Areas of Airways, the Velocity and Divisions of Currents, and the Deductions to be made for Friction. 1. An airway I,oooft. long and sft. by 16ft., having a current of 18,000 cubic feet of air per minute ; if the head coal were taken down so that it measures 16ft. by 10ft., what volume of air will pass, other conditions remaining the same ? 2. What do you consider a dangerous velocity for the air in a highly-explosive mixture of air and firedamp ? 3. An air-course 600 ft. long and Bft. by 10ft. has a current of 10,000 cubic feet of air passing per minute: this is split into two, measuring 460 ft. by 10ft. by 12ft. and 900 ft. by 10ft. by 15ft.; now much will each split pass, and what difference will the water-gauge show ? 4. What form of airway offers the least resistance, and why ? What is a regulator and an overcast ? 5. An airway measures B,oooft. long by 12ft. by sft., and passes 7,500 cubic feet of air per minute, what is the amount of pressure per square foot, and what pressure would be required to produce 12,000 cubic feet per minute?

Fiest-class Ceetificates.—Second Day.—Time : 9 a.m. to 12 noon. V.—On the Nature and Composition of Explosive and Dangerous Gases occurring in Goal-mines, and on Spontaneous Combustion. 1. What is the difference in the effect of breathing carbonic acid and carbonic oxide? What is the specific gravity of the latter, and is it inflammable or not ? Does it put out the flame ? 2. What is the composition of afterdamp? Explain in what ways it is likely to affect the exploring parties. 3. How can you detect the presence of firedamp in large and small proportions? What is its most dangerous volume in relation to air ? 4. Explain fully the bearing of coal-dust on explosions, Is it explosive by itself? How would you cope with it in a mine where it was plentiful and finely divided. 5. How would you detect the starting of spontaneous combustion in a mine or blocked off district, and what steps would you take ? Explain its mode of origin, and how iron-pyrites in the coal affects it. Has any other condition of the mine an important bearing on its occurrence ? What would you do when it had got a firm hold ?

VII. — The Haulage on Planes and in Shafts, also the different Systems of Underground Haulage, with Horse-power required to do the Work. 1. The workings of a colliery have extended far from the pit-bottom, the roads are winding, and the pillars worked out: how would you draw the coal ? Explain fully, and give detailed sketch; dip variable. 2. An incline dips at an angle of 1 in 6, length 30 chains, up which must be drawn 180 tons per day, what system of haulage would you use, and how prevent runaways ? 3. Explain the merits of wheels loose on axle and keyed fast on same. 4. What angle of inclination is most suitable for a self-acting incline ? and sketch how you would connect same with main drawing-road, both with large outputs. What is the best angle to lay off road for drawing by hand ? 5. An endless rope draws 200 tons per day of eight hours up 40 chains at 1 in 8, what horse-power is required, and what is the loss by friction? Assume your own weights for boxes, rope, &c.

Time : 2 p.m. to 5 p.m. VI. — On the Drainage of Mines, and Pumping Appliances. 1. Why are columns of pipes divided into lifts? 2. Show by sketch how you would arrange your lifts and lodgments for a shaft 100 fathoms deep. What size of pipes would you use in such a shaft to draw 10,000 gallons per hour ? Detail calculations. 3. Explain the principle of the (1) syphon, (2) of the pulsometer, (3) any double-action forcepump you are acquainted with. 4. What form of pump would you use to throw 160,000 gallons per day from a depth of 170 ft.? Give sketch, and explain its action. 5. What is (1) a clack-piece ; (2) a working-barrel; (3) how are the pipes supported in the shaft; and (4) to what ? Give sketch. 6. A rising main is 960 ft. deep, what thickness of metal would you use for lOin. pipes ? 7. With plunger-stroke of 6ft., six strokes per minute, and a 12in. working-barrel, what would be the discharge in gallons per 12 hours ?