316 SCIENCE PROGRESS. 



or 165 kilowatts, at the very slow speed of 45 revolu- 

 tions per minute : the dynamos have twelve poles, and 

 thirty-six carbon brushes are used to collect the current. 

 The gradient reaches in places 25 per cent., and each car has 

 two four-pole motors giving 30 horsepower at 600 revolutions 

 per minute, their speed being reduced by double gearing 

 to 50 revolutions of the wheels. 1 



In the transmission of power, properly so called, by 

 continuous currents, much has been done since the pioneer 

 installation by which, in 1886, 50 horsepower was trans- 

 mitted a distance of five miles from Kriegstetten to Solo- 

 thurn : in this case the three-wire system was employed 

 with two generators and two motors each of 1000 volts, 

 and the over-all efficiency of the plant was 75 per cent., a 

 result which at that time was regarded as little short of 

 marvellous. It was erected by the Oerlikon Company of 

 Switzerland, and in the succeeding years the same company 

 followed up their first venture by a number of installations 

 of various horsepowers, large and small. Among these 

 may be mentioned the transmission of 60 horsepower over 

 five miles at Lake Lugano, and of roo horsepower for one 

 mile near Aichberg in the Tyrol with an efficiency of 80 

 per cent, also with a pressure of 1000 volts. In 1891 

 they completed the important transmission of 600 horse- 

 power for a distance of 750 yards at Schaffhausen, where the 

 Falls of the Rhine supply the power. Each turbine of 350 

 horsepower was connected by means of bevel wheels and 

 ropes to a six-pole dynamo with an output of 624 volts and 

 330 amperes at 200 revolutions per minute. At the spinning 

 mills, to which the power is transmitted, there are two 

 small motors of 60 horsepower each and one large double 

 motor giving 380 horsepower. A commercial efficiency at 

 full load of 78 per cent, was guaranteed by the makers. ~ 

 Finally mention must be made of the very important installa- 

 tion by which as much as 1000 horsepower is obtained from 



1 Elektrotechnische Zeitschrift, No. 21, p. 289, 1894. 



2 Kapp's Cantor lectures on The Electric Transmission of Energy, de- 

 livered before the Society of Arts, 1891. 



