Feb. 17, 1888.] 



SCIENTIFIC NEAVS. 



i6c 



Many schemes have been propounded for distributing 

 power in manufacturing districts by means of steam, 

 compressed air, and water pressure, each ot which is in 

 use to a somewhat limited extent ; and as all of them have 

 been known long enough, it may seemingly be inferred 

 from their limited employment that there is not much to 

 recommend their extended use commercially. With 

 steam the condensation in the pipes causes loss of 

 pressure, and results in wet steam being supplied to the 

 engines. Compressed air cannot efficiently be worked 

 expansively, and is attended with loss of heat in the com- 

 pressor. \Vater pressure commonly involves using the 

 maximum power, whatever the work required. Besides 

 these prominent faults of the three several methods, what 

 is of the greatest importance and common to all three is 

 that the generating plant has to be used almost exclu- 

 sively for supplying the power, and cannot be utilised for 

 other purposes in addition ; whereas, with a central 

 electric station, the engines and dynamos serve to 

 generate current for lighting purposes also at night. In 

 collieries electricity will be largely adopted in the near 

 future. For underground hauling, pumping, ventilating, 

 and drilling it can be readily applied with an efficiency 

 double that of compressed air. With a well-arranged 

 installation, 75 per cent, of the brake power of the engine 

 will be utilised on the shaft of the motor. For hauling 

 and pumping, wire ropes or rods are the greatest com- 

 petitors of electricity, which obviates the following dis- 

 advantages in connection with them : — chance of break- 

 down through strain ; wear and tear ; mishap to guides 

 through falls of roof or dirt ; trouble and expense of oiling 

 the guides ; and room required at pit mouth or at bottom 

 for engine, pulleys or levers, or other gear. As the ten- 

 dency in mines in this country is towards a reduction of 

 working hours, the question of mechanical haulage 

 becomes most important, because horses must be fed 

 whether at work or idle, and the cost of haulage by horses 

 therefore increases as the working hours become reduced. 

 For ventilating and drilling, compressed air is perhaps 

 more largely used ; and one of the great points in its 

 favour is that the exhaust is available for supplying 

 fresh air to the miners, and for driving out the foul gas 

 after the firing of shots. But the cost of the compressed 

 air machinery is heavy, as is also that of the pipes for 

 conducting the compressed air from the compressor to 

 the place where it is used. The cost of electric plant is 

 somewhat less, and the efficiency is very much greater ; 

 while by using old haulage ropes as conductors the cost 

 of this item is rendered very small. 



Duprez succeeded in demonstrating practically that 52 

 horse-power could be transmitted over a distance of 35 

 miles, namely from Creil to Paris, through a copper 

 cable equal in section to a wire of less than o'2 diame- 

 ter. But his machmes were not efficient, the power re- 

 quired to drive the dynamo being 116 hp., of which 44 

 per cent, was lost in the dynamo and motor, and 1 1 per 

 cent, in the 70 miles of the outward and return wire. 

 There is no reason however why much more efficient 

 results should not have been obtained ; as much as 18 

 per cent, of the total power was absorbed for maintain- 

 ing the magnetism of the field of the dynamo, whereas 

 in a well-designed machine less than 5 per cent, should 

 suffice. Mr. C. E. H. Brown, of Oerlikon, has succeeded 

 in transmitting by electricity 50 horse-power from water 

 power at Kriegstetten over a distance of 5 miles to Solo- 

 thurn in Switzerland, with a commercial return of over 

 70 per cent. 



At Hatfield, on the Marquis of Salisbury's estate, the 

 River Lea is utilised to generate electricity, which is 

 transmitted to the house and over the estate for a variety 

 of purposes. Two turbines are used : one to drive a 

 40-h.p. Siemens alternating-current dynamo, for lighting 

 the house; and the other to drive a i6-h.p. Brush 

 machine, for arc-lighting at night, and in the day for 

 working the motors at the house and on the farm. Those 

 at the house drive pumping and ice-making machinery, 

 and a 24 in. Blackman air-propeller fixed in the roof for 

 ventilating ; on the farm the motors are used for elevat- 

 ing hay and corn sheaves to the tops of the stacks, for 

 thrashing, for cutting rough grass with a chaff-cutting 

 machine for ensilage, in fields extending to a distance of 

 two miles, for grinding corn, etc., to make fodder, and for 

 other purposes. The m.otors have also been used for 

 pile driving, for making cofferdams where necessary in 

 the river; and also for dredging the river and clearing it 

 of weeds. A Gramme motor, capable of raising 2,500 

 to 3,000 gallons per hour, pumps the town sewage into a 

 tank at a height cf 30 ft. for irrigation. The conductors 

 are carried overhead on poles about the farm, and under- 

 ground in wooden troughs to the house. 



The practical methods of accomplishing electric loco- 

 motion seem to the author to be the four follow- 

 ing : — 



Firstly, the use of a third insulated rail or conductor 

 to convey the current from the generator to the motor 

 carried on the locomotive, contact being made by a wheel 

 or a sliding spring or brush ; while the two ordinary 

 rails serve as a return circuit, the current being con- 

 ducted from the motor to the rails through the frame, 

 axle, and wheels of the locomotive. 



Secondly, the employment of an overhead conductor 

 supported on poles or from the roof of an arch or tunnel, 

 contact being made either by a carrier on wheels running 

 along the conductor, or by rubbing. The return circuit 

 may be either through a second overhead conductor, or 

 through the ordinary rails as in the third-rail plan. 



Thirdly, the use of an underground insulated con- 

 ductor, placed in a conduit between the rails, and con- 

 ducting the current from the generator through a contact 

 carriage to the motor, whence it is conveyed back through 

 the frame, axles, wheels, and rails. 



Fourthly, the employment of storage batteries, placed 

 preferably under the seats of the car, with the motor 

 and gear underneath, or the whole placed on a separate 

 locomotive. 



The plan of using the ordinary rails as positive and 

 negative conductors, and insulating the wheels or axles of 

 the cars, is attended with the objection that, owing to the 

 rail supports having to carry heavy loads, there is diffi- 

 culty in insulating the rails sufficiently to prevent exces- 

 sive leakage to earth. 



Of these four methods the first two are the cheapest 

 and most efficient, but are applicable only to railroads : 

 while the two other plans, of an underground insulated 

 conductor, and of storage cells on the car, are both 

 applicable to street tramways. 



The plan of transporting material in skips on overhead 

 wire-ropes by means of electricity, introduced under the 

 name of telpherage by the late Professor Fleeming Jenkin, 

 of Edinburgh, has not so great a field for its use in this 

 country as it may have in less populous regions, because 

 our roads are good, and railways generally near at hand, 

 and we have abundance of water carriage. But in places 

 where material has to be conveyed across hilly districts 



