& Co. decided to put down a larger plant, to deliver 120 gallons per minute through 900 feet of vertical head, and I was intrusted with the designs of the machines. This larger plant was started in February of the following year, 1888, and has continued running about 22 hours per day since then. The run now exceeds 18 months, and during that period there have been no breakdowns traceable to the electrical details, all stoppages being due to mechanical defects, incidental generally to the engine and pumps. The plant has been described before, but not in detail. I now propose to give results of tests made by the colliery engineer, Mr E. Brown, and myself. The engine is of the semi-fixed type by Robey & Co., of Lincoln. It is compound and is rated by the makers at 30 nominal horse-power. It has indicated during the past 18 months on an average about 80 horse-power. The dynamo is driven off the fly-wheel by a link belt 14 inches wide, curved to fit the pulley. The belt speed is about 2750 feet per minute. The dynamo is designed to give 600 volts and 70 amperes. The motor is of similar design to the dynamo, but the fieldmagnets are of lighter construction. The pumps are differential, with two 6-inch and 4-inch rams. The suction is made by the two large rams only. On the instroke the 6-inch rams deliver water partly into the rising main and partly into the small rams. On the out or suction-stroke the 4-inch rams deliver into the column and so the discharge is fairly continuous. When doing full duty, the pumps make 25 revolutions per minute. The rising main is about 450 yards long, and is composed of 4-inch cast-iron pipes. An air-vessel about 5 feet high is fitted at the lower end near the delivery-clacks. The piping is undoubtedly too small for 120 gallons per minute. It was really designed for a feeder of about 50 gallons. The water travels in the column at about 250 feet per minute, and there is nearly 10 horse-power lost in friction. This heavy loss is against the total efficiency of the plant, and an allowance can be made if any one thinks proper. The cable is built of 19 strands of No. 17 B. W. G. copper wire, insulated and lead-covered. It is about 1000 yards long, and has a resistance of about .5 of an ohm.

About one week after the erection in February, 1887, the electrical quantities for the full load averaged about 65 amperes and 603 volts, with 450 revolutions of the dynamo and 134 revolutions of the engine per minute. The motor ran at about 450 revolutions per minute, and the pumps at 25 revolutions. Under the above conditions the water delivered was measured and found to be between 118 and 120 gallons per minute. The suction has a rise of about 14 feet, and the column is 860 feet in vertical height. Thus the theoretical horse-power in the water is about 32. The engine was indicated at the same time, and found to be giving 80 horse-power. The efficiency of the system, that is, the ratio between theoretical work in the water and indicated horse-power of engine, was therefore equal to 40 per cent. These tests have been repeated from time to time by various gentlemen, and the readings show a gradual decrease of the losses due to friction, particularly in the engine and pumps. A log has been kept, and the daily readings of current show a steady fall. At the last test, Mr. E. Brown found the current had fallen to about 62 amperes, and the engine only indicated about 73 horse-power. The efficiency had thus increased to about 40 per cent.

The figures of the tests are as follows:

=

The percentage of losses, as calculated from the indicator cards, are:

The engine doing above load indicated 73.0 horse-power. The friction of the water in the pumps and rising main is arrived at by subtracting the sum of the theoretical horse-power in the water delivered, and the total friction, from the total indicated horse-power of the engine; or, 73 —(31.5+ 28.6) 12.9. This is not quite correct. The friction diagrams are necessarily taken with no load on the pumps, and hence are all slightly lower than is actually the case when the load is on. From the known efficiency of the motor, the loss in the pumps and rising main has been found to be not less than 10 horse-power. The coal consumption of this plant was 80 much less than that which obtained with the compressed air-plant formerly used for the same work, that at my suggestion careful tests were made of the air-plant efficiency.

The conditions were singularly favorable for comparison. The superseded air

engine was still in position, and could be coupled to the same pumps. There were also two sets of compressors-a pair of horizontal compressors 20 inches by 4 feet, and a large vertical one. These were each put to drive the pumps, but since the pressure obtainable was only sufficient to raise the water about 530 feet, the columir was tapped at the Stanley Main seam. Tests of the electrical plant delivering to the same place were also made, with the following results: The horizontal compressors gave a net result of 12 per cent., and the vertical one gave a little over 14 per cent., while the electrical system returned 44.4 per cent. The figures of the latter test are as follows:

These last tests were all made by the colliery engineer, Mr. E. Brown. The results obtained were so satisfactory that the pumps were at work only a fortnight before Messrs. Locke & Co. gave an order for a duplicate set of electrical plant, intending to use the new machines for both hauling and pumping. The pair of 20 inches by 4 feet compressors were removed, and foundations were laid in their place for the two dynamos, the old air-compressing engines, 20.5 inches by 4 feet, being arranged by suitable gearing to run them. At the same time a set of three throw rams, 6 inches bore by 12 inches stroke, were specially designed for dealing with the water. This new plant was nearly all finished and delivered at the colliery by the early part of the present year, but press of circumstances prevented the starting of the engines till late in July. The new dynamo, motor and pumps show a further decrease of power for the same work. The quantities average about as follows: Engine, 50 revolutions per minute; dynamo, 480 revolutions per minute; 690 volts and 59 amperes motor, 450 revolutions per minute; pumps, 34 revolutions per minute; water delivered, about 125 gallons per minute. The arrangement of the motor-house is very complete. A main shaft is run through the three houses containing the two pumps and the hauling gear. This shaft is fitted with clutches, so that either motor can be coupled to either of the pumps or the hauling-sheaves.

Or both motors can be coupled to the shaft, and all or any of the machines attached. It is a most convenient and efficient arrangement, and prevents a trivial accident resulting in a serious stop to the mine.

. The following are the particulars of the endless rope haulage: The main or belt rope makes three turns round the main driving sheave, and then passing round a tightening sheave, is led through a short tunnel to the main road. Here it gives motion to two horizontal sheaves, making about two and a half turns round each. These sheaves are coupled to two endless ropes by friction cones, worked by screwgear. The main rope is kept running at the desired speed, and the two working ropes are started and stopped as necessary. The main rope is 1 inch in diameter. The working ropes are both of an inch. They are all made of crucible steel. The sheaves are all about 4 feet 4 inches in diameter over the iron lagging. The coal now delivered is about 400 tons per day of eight to ten hours, the "Haighmoor" rope only being used. The motor is running at about half the arranged speed, and is doing less than half its designed output. The "Kirkthorpe" rope will be put on next week. Even with this additional load of some 300 tons per day, there is an ample margin for future increase of output. The arrangement could easily deliver 1000 to 1200 tons per day if necessary. No difficulty of any kind has been experienced with the hauling details. The ropes work with the regularity of clock-work, maintaining an almost constant speed whatever the load may be. The dynamo and motor are running most satisfactorily indeed; without looking at the ammeter, it is hardly possible to say whether the working rope is on or not.

Exception may be taken to the tests of these air plants on the score of the compressors being old and out of order. Indeed, I admit that the efficiency should be nearer 20 per cent. with plants of modern design in good order.

In comparison with compressed-air systems, the efficiency of an electric installation gives it an important advantage. I may refer, for instance, to the following test of the compressed-air system at the Chapin & Ludington mines, Iron Mountain, Mich. These mines are 3 miles from the falls which supply the power. There are four turbines at the falls, one of 1000 horse-power and three of 900 horsepower each; total, 3700 horse-power. The pressure is 60 pounds at 60° Fahr. Each turbine runs a pair of compressors. The pipe to the mines is 24 inches in diameter. The power is applied at the mines to Corliss engines, running pumps, hoists, etc., and direct to rock-drills.

The plant cost $100,000 (estimated). A test made February 20, 1888, gave 1430.27 horse-power at the compressors, and 390.17 horse-power as the sum of the horse-power of the engines at the mines. Therefore, only 27 per cent. of the power generated was recovered at the mines. This includes the loss due to leakage and the loss of energy in heat, but not the friction in the engines or compressors.

In other words, the efficiency of the system as it would be stated for

an electrical plant, does not exceed 25 per cent. The figures above are a fair example of tests which are made at regular intervals.

I venture to think that an electrical plant, to give an effective return of 390 horse-power on the shafts, etc., at the mines, would not have cost more, in this case, than $60,000 at the outside.

I take the foregoing from a paper by Mr. R. P. Rothwell, in the Engineering and Mining Journal of January 5, 1889.

Prof. Kennedy has made a test of the Popp system of pneumatic transmission in Paris. The best efficiencies to be expected seem to be about 20 per cent., even with modern plants.

PECULIAR WORKING OF A BLAST-FURNACE,

BY N. B. WITTMAN, BIRDSBORO, PA.

(Washington Meeting, February, 1890.)

THE working of blast-furnaces is always of interest to many members of the Institute, for which reason I present an account of the working of the furnaces of the E. and G. Brooke Iron Company, of which I have had charge for the past four years. Although there are no phenomenal runs to record, there have been long periods of satisfactory work, and also periods-altogether too long—when one of our furnaces has behaved in a way which may be described as 'nagging." All the conditions were apparently normal, but only a very light burden could be carried, which of course resulted in a high fuel-consumption to the ton of iron, as well as increased cost of labor.

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The two active furnaces of this company have the following dimensions and equipment:

Both furnaces are blown with I. P. Morris condensing-engines, sim