36 Mr. Alexander Siemens [Feb. 3, 



present a strong contrast to the effect steam has had on the develop- 

 ment of industries for the reasons already stated ; and, in addition, 

 there are many cases where the erection of boilers and steam engines, 

 or even of gas engines, would be inadmissible on account of want of 

 space or of the nuisances that are inseparable from them. Motive 

 power will, therefore, be available in a number of instances where up 

 to the present time no mechanical power could be used, but the work 

 had to be done by manual labour or not at all. 



You may have noticed that I have confined my remarks hitherto 

 to the case of distributing electricity over a limited area, but that I 

 have not yet discussed the question of transmitting power to a great 

 distance. 



Theoretically we have been told over and over again that the 

 motive power of the future will be supplied by waterfalls, and that 

 their power can be made available over large areas by means of 

 electric currents. As a prominent example, the installation is con- 

 stantly mentioned by which the power of a turbine at Lauffen was 

 transmitted over a distance of 1 10 statute miles to the Frankfurt 

 Exhibition with an efficiency of 75 per cent. No doubt this result is 

 very gratifying from a purely scientific point of view, but, unfortu- 

 nately, in practical life only commercially successful applications of 

 science will have a lasting influence, and in this respect the Lauffen 

 installation left much to be desired. 



On the one hand science tells us that the section of the conductor 

 can be diminished as the pressure of electricity is increased, and it 

 appears to be only necessary to construct apparatus for generating 

 electricity at a sufficiently high pressure so as to reduce the cost of a 

 long conductor to reasonable limits. On the other hand, experience 

 shows that at these high potentials the insulation of the electric 

 current becomes a most difficult problem, and for practical purposes 

 difficulty means an increased outlay of money. As an illustration of 

 the difficulties encountered in the employment of high-tension currents, 

 I can demonstrate to you that many of the insulating materials em- 

 ployed with success for low-pressure currents break down under the 

 strain of high-pressure electricity. 



For the purpose of these experiments the current of electricity 

 delivered by the street main at a pressure of 2400 volts is diverted 

 to a large transformer placed on the ground-floor, and from there it is 

 led through a twin cable to this room at a pressure which can be in- 

 creased up to 50,000 volts. This twin cable was used in 1891 at the 

 Frankfurt Exhibition, for conveying a current of 20,000 volts from 

 the main Exhibition to the Exhibition on the Main, and when it was 

 returned to the works, it was found that the insulation was as good as 

 when it was first manufactured. A sample of it lies on the table, 

 and by its side the sample of a concentric cable designed for a current 

 of 2500 volts. A comparison of the two shows in a striking manner 

 how elaborately high-tension cables have to be insulated. 



