August ii, 1892] 



NATURE 



359 



and hauling gear, became obvious. But, with intermittent 

 working machines, there rose the need of an appliance for 

 storing energy during periods of minimum demand and restoring 

 it in periods of maximum demand. The invention of the accu- 

 mulator by Lord Armstrong made the system of hydraulic 

 transmission a success, and at the same time fixed its character 

 as a system specially adapted for those cases where intermittent 

 work is required to be done. Lord Armstrong's system of 

 hydraulic distribution by water at a pressure of 700 or 8od lbs. 

 per square inch, with the use of accumulators for equalizing the 

 variations of supply and demand, has now been widely adopted. 

 The most extensive scheme of that kind hitherto executed is the 

 important scheme carried out by the Hydraulic Power Company. 

 Over fifty miles of pressure mains have now been laid in the 

 streets of London. The Falcon Wharf pumping station con- 

 tains four sets of compound pumping engines, each of 200 horse- 

 power. Two additional pumping stations have now been 

 erected, and 1500 lifts are worked from the pressure mains. 

 The minimum charge for water is 2j. per 1000 gallons. This 

 rate of charge is economical for such machines as lifts, but it 

 would be extravagant for machines working continuously. It 

 would be equivalent to a charge of nearly ;^5o per horse-power 

 per year of 3000 working hours, apart from interest and main- 

 tenance of machines. 



I shall indicate later on that in some cases where local con- 

 ditions are favourable, where there is cheap water-power, and 

 the possibility of constructing high-level storage reservoirs, then 

 hydraulic transmission can be adopted with success for distribu- 

 ting power for ordinary manufacturing purposes. But neither 

 telodynamic transmission nor hydraulic transmission have proved 

 suitable as methods for the general distribution of motive power 

 from central stations. Distribution by steam and distribution | 

 by heated water have both been tried in the United States, but 

 not with very remarkable success. Only two other methods are 

 available — distribution by compressed air and distribution by ■ 

 electricity. 



For many years compressed air has been used to distribute 

 power in tunnelling and mining operations to considerable j 

 distances. It is only recently that it has been used as a general 

 method of distributing power to many consumers. In many 

 installations the machinery has been rough and unscientific, and ■ 

 the waste of energy very considerable. It is through experience , 

 gained and improvements carried out in the remarkable system 

 now at work in Paris, and known as the Popp system, that the 

 great advantages of compressed air distribution have been proved. 

 The Paris system has very gradually developed. About 1870 a 

 small compressing station was erected to actuate public and 

 private clocks by intermittent pulses of air conveyed along pipes 

 chiefly laid in the sewers. In 1889 about 8000 clocks were 

 thus driven. Meanwhile the compressed air had also been 

 applied to drive motors for small industries. The demand for 

 power thus supplied grew so rapidly that a second compressing 

 station wasbuUt in the Ruede Saint Fargeau. In 1889 steam 

 air compressors of 2000 horse-power were at work, and 

 additional compressors were under c instruction. The pressure 

 at that time was five atmospheres, and the largest air mains were 

 12 inches in diameter. Ingenious and simple rotary machines 

 were used as air motors for small powers, and for larger powers 

 any ordinary steam-engine was converted into an air motor. 

 Prof. Kennedy made tests in 1889, which were communicated j 

 to this Association. He found that a motor four miles from the 

 compressing station indicated 10 horse-power for 20 indicated | 

 horse power expended at the compressing station, an efficiency j 

 of 50 per cent. only. There were then 225 motors worked from I 

 the air mains. 



Since 1889 more extended investigations have been made by j 

 Professor Kiedler, of Berlin, and the chief part of the waste of 

 work has been traced to inefficiency of the air compressors. 

 Compound air compressors of much higher efficiency have now 

 been constructed. The plant at the Saint Fargeau station has 

 been increased to 4000 horse-power. A new station has been ! 

 erected on the (^uai de la Gare, intended ultimately to contain 

 compressors of 24,000 horse-power. Compressors of 10,000 1 

 liorse-power are already under construction. ] 



Compressed air transmission, whether or not it is the most 

 economical system, is undoubtedly applicable for the distribu- 

 tion of power on a very large scale and to very considerable dis- 

 tances. There is nothing in any of the appliances which is 

 novel or imperfectly understood. The air is used in the con- 

 sumer's premises in machinery of well-understood types, and 



NO. I 1 89, VOL. 46] 



old steam engines can be converted into air motors without 

 difficulty and without alteration of existing transmissive 

 machinery in the factories. Not least important, the air can 

 be measured with accuracy enough for practical purposes by 

 simple meters, and charged for in proportion to the power con- 

 sumed. Air compressors and air motors are not as efficient as 

 dynamos and electric motors, but in one respect distribution by 

 air and electricity are similar. For distances which are not 

 more than a few miles the loss of energy in transmission is small 

 enough to be insignificant. 



There is yet one other mode of power distribution which 

 promises to become the most important of all, and which, in 

 the case of transmission to very great distances, if such trans- 

 mission becomes necessary, has undoubtedly great advantages 

 over every other method. 



About electrical distribution of power I shall not venture to 

 say much, partly because I am not an electrical expert, partly 

 because it has been lately pretty fully discussed. In the United 

 States there has been an enormous development of electric 

 tramways, which are essentially cases of electric power distri- 

 bution. In this country we have the South London and some 

 other railways worked electrically. There are others also on 

 the Continent. But electrical power distribution to private 

 consumers for industrial purposes has not yet made as much 

 progress as might have been expected. Perhaps electrical en- 

 gineers have been so busy with problems of electric lighting that 

 they have had no time to settle the corresponding problems of 

 power distribution. 



No doubt continuous current distribution presents at the 

 moment the fewest difficulties, or, at any rate, involves the fewest 

 comparatively untried expedients. Several continuous-current 

 plants for distributing power are in operation, of which perhaps 

 the most interesting is that at Oyonaz, which was described in 

 Section G last year by Prof. G. Forbes. There 300 horse- 

 power obtained by turbines is transmitted 8 kilometres at 1800 

 volts. It is then let down by motor transformers to a voltage 

 suitable for lighting and driving motors. A number of small 

 workshops are driven, the power being supplied at a fixed rent. 



At the Calumet and Hecla mines on Lake Superior, at the 

 Dalmatia mines in California, and some other places, energy 

 derived from turbines is transmitted distances of a mile or two 

 by continuous electric currents and used in driving mining ma- 

 chinery, and some cases of the use of electrical distribution in 

 mines in this country were mentioned by my predecessor in his 

 address last year. 



At Bradford a few electric motors are being worked from the 

 electric lighting mains. The largest of these is of twenty horse- 

 power. The price at which the electricity is supplied is not 

 given, but I believe the cost is high when reckoned for con- 

 tinuous working. It would seem that it must be so when the 

 electric current is generated by steam power. 



At Schaffhausen an electric transmission has now been con- 

 structed alongside of the wire-rope transmission. The power is 

 derived from two turbines, and is ttansmitted across the Rhine, 

 a distance of 750 yards, at 624 volts. The current drives a 

 spinning-mill, in which the largest motor is 380 horse-power. 

 The power is sold, I believe, at £1, per horse-power of the 

 motors per annum. 



Many engineers have now apparently come to the conclusion 

 that alternating currents will be belter for power transmission 

 to considerable distances than continuous currents. One inter- 

 esting alternate current transmission, partly for power, partly for 

 lighting purposes, has been for some time in operation at 

 Genoa. 



On the line of the aqueduct bringing water from the Gorzente 

 rivulet three electric stations are being established. The reser- 

 voirs are 2050 feet above Genoa, and as this is a much greater 

 fall than is required for water-supply purposes, part can be used 

 to gent-rate about 1600 horse-power. 



In the first of the power stations erected there are turbines of 

 450 horse- power driving two dynamos. A second larger station 

 was completed in November. In this there are eight alternate- 

 current dynamos of 70 horse-power each. Six alternators are 

 worked in series, transmitting a current of 6000 volts. The 

 current is transmitted sixteen miles by bare copper wires, 

 8 '5 mm. diameter, placed overhead. The current is used both 

 for lighting and power purposes. 



Another method of using alternating currents was adopted in 

 the remarkable experiment at Frankfort last year. In that 

 case energy obtained by turbines at Lauffen was transmitted to 



