ON THE PROGRESS OF ELECTRIC LIGHTING. 15 



original research ; if the nation is encouraging it in a manner we may well be 

 proud of, the fact is due in no small degree to the efforts of those, many of them 

 members of this Society, who have made practical ends a means, rather than to 

 those who would make science more exclusive and who are indifferent to practi- 

 cal ends or popular sympathy. Such at least is my apology for the nature of 

 this paper. 



PHYSICS. 



ON THE PROGRESS OF ELECTRIC LIGHTING, i 



WILLIAM HENRY PREECE, F.R.S. 



I propose briefly to indicate some of the progress made, both in a scientific 

 and practical sense, and to show that electric lighting is a real, true success. 



>t: * :^< >H ^ >f; jjc 



As regards the scientific progress little has to be said. We had learned 

 nearly all we wanted to know before electric lighting had entered its practical 

 stage. In reality, the very fact that it had entered its practical age was a proof 

 that it had passed through its infancy of scientific tuition. The conditions that 

 determined its production, the laws that regulated its behavior, the means that 

 were available for its control, had all been thoroughly investigated and laid down 

 before practice stepped in to show us what could be done. 



Electricity can be produced, currents can be distributed, light can be gener- 

 ated, but we have yet to learn how all this can be supplied economically, profita- 

 bly, and with safety to person and to property. Practice alone can determine 

 these points, and it is well to make a rapid survey of the extent to which practice 

 has up to now enabled us to solve these points. The future of electric lighting is 

 now in the hands of practical men. 



Electric lighting has called for motors of a class not hitherto in demand, 

 and steam, gas, and water engineers have rushed to the front to meet the demand. 

 The production of electric currents means the expenditure of power ; and when 

 the extent of the installation is known, it is a simple calculation to specify how 

 much horse-power is needed. Some employ a fall of water to urge a turbine, 

 others employ steam, many use gas to obtain the power requisite to convert the 

 energy of mechanical motion into that of electric currents. Gas-engines are be- 

 ing very largely used, and since the expenditure of a given amount of gas as 

 power, will produce more light through the agency of electricity than by direct 

 combustion in air, it is clear that we have here an evidence of the true function 

 of gas. The perfect gas-engine has not yet been produced. Those in use are 



1. Paper read before the Society of Arts, London, March 5, 1884. 



