450 POPULAR LECTURES AND ADDRESSES. 



by myself in my " replenisher " for multiplying 

 and maintaining charges in Leyden jars for 

 heterostatic electrometers, and in the electrifier 

 for the siphon of my recorder for submarine 

 cables. 



The dynamos of Gramme and Siemens, invented 

 and made in the course of these fourteen years 

 since the discovery of the fundamental principle, 

 give now a ready means of realising economically 

 on a large scale, for many important practical 

 applications, the old thermo-dynamics of Joule in 

 electro-magnetism ; and, what particularly concerns 

 us now in connection with my present subject, they 

 make it possible to transmit electro-magnetically 

 the work of waterfalls through long insulated con- 

 ducting wires, and use it at distances of fifties or 

 hundreds of miles from the source, with excellent 

 economy better economy, indeed, in respect to 

 proportion of energy used to energy dissipated 

 than almost anything known in ordinary mechanics 

 and hydraulics for distances of hundreds of yards 

 instead of hundreds of miles. 



