compression and intercooling with higher pressures, give an efficiency 40 per cent. better than was obtained a few years ago. Electricity (with some reservation in the case of very fiery mines) is of marvellous adaptability to every requirement in mining. It is economically produced, easily distributed, and its efficiency at ordinary loads may be taken as 68 per cent. in actual work given out by the motor-shaft, the losses being 12 per cent. in the engine, 10 per cent. in the dynamo, 5 per cent. in the line, and 10 per cent. in the motor. In American mines, electricity is in universal use, and latterly, I am pleased to say, has been receiving more attention in this country. A saving of 8d. per ton has been recently recorded at a large north-country colliery by its adoption in a thorough manner. In displacing scattered engines, an economy of 25 per cent. to 30 per cent. may be assured, and in workshops 35 per cent. to 50 per cent. as against belt-and-shaft drives. Collieries are generating current at d. per Board of Trade unit, but this figure can be reduced, as I hope presently to show. Its use underground cannot be too rigorously safeguarded, for although with three-phase current, properly insulated and armoured cables, gas-tight junction-boxes and switch-boxes, and enclosed or sparkless motors, safety may be to a large extent assured, there are still grave possibilities of accident. The spark of an ordinary signal-bell will ignite fire-damp; and I feel constrained to say here that the practical study of electricity by those responsible for its introduction does not always receive the attention that it demands. It would be most unfortunate if any indiscretion in its use should result in disaster, thereby tending to check the employment of this most important factor in future economy and efficiency.

:

Another direction in which we may look for great economy is in the employment of coal-cutting machinery. The output per man in the United States is 82 per cent. more than in the United Kingdom, and this is greatly due to their mining coal by machinery pits so operated showing more than double our output per man. They use largely the original British machines, but have improved and adapted them to their requirements, and evolved other types. While we employ under 400 machines, they have 3,500 in regular work, and when we see outputs of 11, 3 and 34 tons per man increased to 4, 63 and 8 tons, and savings of 4d, to

VOL. XXIV-1902-1903.

11

over 1s. per ton effected, we cannot afford idly to wait and doubt. These are results that we see in our own collieries, and it is surprising that so many, with conditions admirably suited to machinery, are doing absolutely nothing in this direction. It is unfortunatein North Staffordshire that many of us have to struggle on under conditions which render the use of any machine, so far produced, impracticable. Seams lying at angles of 30 to 50 degrees with as many faults as roadways, present almost insurmountable difficulties to the successful introduction of coal-cutting appli

ances.

A most important advantage following the use of such machinery is the abolition or minimizing of blasting, and in this connection I must refer to the hydraulic wedge shown to the members by Mr. James Tonge a few years ago,* for which he has received the Society of Arts prize and medal. I have seen a man with this machine getting 30 shots a shift with his can of water instead of a canister of explosive, and we appear to have, at last, a really practicable tool.

Turning to our iron-industry, let me say a few words regarding another serious waste-that of the gases from our blast-furnaces. The blast-furnace is a gas-producer of the highest order, its inherent heat doing the work of melting the ore, and generating at the same time 160,000 to 200,000 cubic feet of combustible gas per ton of fuel consumed. The gas has a heat-value of about 100 British thermal units per cubic foot, and 100 to 120 cubic feet in a gas-engine will give 1 horsepower. The gas-engine is now a thoroughly practical, reliable and simple machine. We have 70,000 engines working in this country, chiefly with illuminating or producer-gases. But on the Continent, extraordinary progress. is being made, engines of 1,500 horsepower working with blastfurnace gas, and others of 2,000 and 4,000 horsepower will soon be running, although only two years ago, at the Paris Exhibition, a 600 horsepower engine created great surprise. At one iron- and steel-works in Germany, the furnace-gases are driving nine gasengines, aggregating 5,400 horsepower; and at another, there are several engines of 600 and 1,500 horsepower generating electricity at 550 volts, supplying 64 motors at the steel-works for rolling-mills, locomotives, cranes, hoists, and mechanics' shops, and lighting 240 arc-lamps and 400 incandescent-lamps. In this * Trans. Inst. M. E., 1898, vol. xv., page 269.

country, only two or three works have attempted to employ gas in this way, the majority being content to use it under the boilers, the bulk going to waste, although 100 feet in a gas-engine will give as much power as 400 feet used for raising steam.

Here is a calculation applied to a furnace producing 300 tons of iron per week. The consumption of fuel taken at 1-875 tons per hour would give 303,535 cubic feet of gas, of which one-third would be required for heating the stoves, leaving 197,357 feet for power. Allowing 10 per cent. loss on the total gas, the powerquantity would be 167,004 cubic feet. Taking the heat-value of the gas at 95 British thermal units, and the engines requiring 140 cubic feet per indicated horsepower, and 152 horsepower for the blowing-engines and hoists, there would remain 1,040 horsepower as a continuously available surplus-power.

I will take, however, a lower figure, given by one of the presidents of the Iron and Steel Institute, namely, that for every 100 tons of pig-iron made per day, the surplus gas represents 1,000 horsepower. Applying this to North Staffordshire, assuming that all our 28 blast-furnaces were at work and producing 600,000 tons of iron per annum-certainly not an unreasonable figure-and allowing 32 per cent. for loss by conversion and distribution as electrical energy, we should have a continuous current of 13,600 electrical horsepower. Now Mr. W.N.Atkinson states that we have at our collieries, engines of 30,000 indicated horsepower doing work other than winding coal, this at 10 hours a day at full work would be equal to 12,500 horsepower continuously over a cycle of 24 hours, so that it is evident we should have from our 28 blastfurnaces a surplus power, if taken continuously, equal to doing all the work at our collieries except winding coal. This current if sold at d. per Board of Trade unit, would be worth at 10 hours a day, £65,875 a year, or if for power and lighting for 20 hours a day, £131,750 a year; and to the commercial mind these figures bring visions of dividends. Proportionately, the 350 blastfurnaces now working in the United Kingdom, would give a continuous current of 170,000 electrical horsepower: the whole of the collieries requiring for 10 hours 990,000 horsepower, or the equivalent of 410,000 horsepower continuously. We must, therefore, look for an additional source of supply. We shall find it in our coke-ovens, where there is a similar waste calculated at 251,600 electrical horsepower. Together then, we should have a

surplus of 421,600 electrical horsepower, which if taken continuously would be equivalent to the power required by all the collieries in the United Kingdom, except for winding coal. At d. per Board of Trade unit for 10 hours a day, the current would realize £2,039,800, and for 20 hours a day £4,079,600 per annum, and this is now being wasted. I have in these figures merely brought in the collieries to give point to the case, and it is not necessary for me to show how this surplus-power could be utilized. On the Continent, its importance is well understood, and the savings are realized in the shape of hard cash in pocket.

Coincident with the development of the gas-engine, producergas is asserting its claims to a first place in the economics of power-generation. Compared with steam-plant, the gas-producer returns 75 to 80 per cent. of the thermal value of the coal, or practically the same as a steam-boiler; but the gas-engine returns 15 to 30 per cent. of thermal efficiency, or twice that of the steamengine with 5 to 15 per cent. of thermal efficiency. As fuel only, producer-gas takes a high place. Under steam-boilers, 8 to 10 pounds of water are evaporated per pound of coal in the producer; and in steel-works it may be almost said that modern processes owe their existence to producer-gas. We will consider it, however, more in connection with the gas-engine. Its thermal value varies from 135 to 160 British thermal units per cubic foot, and 140,000 to 160,000 cubic feet of gas are generated per ton of fuel, 60 to 80 cubic feet being consumed per indicated horsepower in the gas-engine, or we may say 2,000 horsepower per ton of fuel, 1 pound of fuel being a safe basis to take as the consumption in a good plant per indicated horsepower-hour.

At the Tees-side engineering-works, monthly returns show 089 pound of fuel per brake horsepower. At Leyton electric power-station, 0·942 pound per indicated horsepower; Uxbridge, 1:067 pounds; Winnington chemical-works, 0·92 pound: Paris, with French coal, 081 pound; and Zurich, 1:22 pounds of fuel per indicated horsepower. At Winnington, a Premier gas-engine of 600 horsepower showed an average over two years of 105 pounds, but at times attained the low figure of 088 pound of fuel per indicated horsepower-hour-the same engine running 138 days without stopping. The use of producer-gas is much more general on the Continent than in Great Britain, the Anzin colliery, France, putting down just now producer-plant for all its work except winding.

The late Mr. Bryan Donkin, whose great experience and ability commands our confidence, reduces the subject to the cost per horsepower of work done.

The fuel-cost only is taken in the above figures, and if we calculate on a consumption of 1 pound of fuel per indicated horsepower-hour, and take slack at 5s. per ton, the cost would be 0026d. I will take, however, for, say a 500 horsepower plant, 1 pounds of slack per indicated horsepower-hour. The cost would be fuel, 0032d.: wages, 0'024d.; and stores, 0012d.; a total of 0.068d. per indicated horsepower-hour. If we generate electricity, and put the mechanical efficiency of the gas-engine at 85 per cent. and dynamo at 90 per cent., or total combined efficiency of 75 per cent., the cost would be 0'09d., or say 0·1d. per electrical horsepower-hour, or 0.14d. per Board of Trade unit. If we make further allowances, and put the cost at 0.20d. per Board of Trade unit, the cost per annum for fuel, wages and stores of a 500 horsepower plant will be under £2,000, a figure so surprisingly low as to arrest our attention, and set us considering the possibilities of economy by adopting power-gas. There will be no economy in taking power from central stations. Any colliery may have its own plant, the gas being preferably distributed for surface-work, and electricity used for distant and underground work.

I had intended to refer to other possible economies relating to work underground; and, in connection with our difficulties in meeting American competition, to compare our respective railway and transport-facilities, but time will not permit. I trust however, that what I have said may suggest to the members subjects for papers and profitable discussion during the short time that I shall have the honour to occupy the Presidential chair.