21 



would complete the circuit ; the wonderful Morse printing tele- 

 graph ; and the culminating improvement of the Hughes type- 

 writing instrument, which flashes the message to its far destina- 

 tion at the moment the operator touches the magic keys. Before 

 passing on to the marvels of "wireless" telegraphy, the Lecturer 

 stayed to say a few words about submarine cables, — "the nervous 

 system of the world," as he called them. The difficulty with 

 long-distance cables was at first a commercial one. They cost a 

 lot of money, and business men wanted to know at what rate 

 they would deliver the messages sent over them. At long dis- 

 tances the effect of the current was very much lessened, and the 

 problem of how to receive the messages was for some time a 

 difflcult one. Then, with admirable clearness, the Lecturer 

 explained, by means of a diagram, Lord Kelvin's beautifully 

 ingenious invention of the refracting galvanometer, in which 

 the almost imperceptible oscillations of a tiny needle of watch- 

 spring steel, enclosed in a circuit at the receiving end, are 

 magnified and made readable to the operator by means of a 

 strong ray of light thrown upon and again reflected from it. 

 As a fitting climax to the description of telegraphy with wires, 

 the facsimile of an Atlantic cable message as written by another 

 of Lord Kelvin's machines was thrown on the sheet. " Upon 

 the whole, it isn't worse than some persons' handwriting," com- 

 mented the Lecturer on the weird lines that zigzagged across the 

 paper. 



The second part of the subject was opened by an eulogy of 

 Faraday, " the father of modern electricity," who, in the early 

 part of the century, used to go day by day to his laboratory, with 

 the regularity of a business man to his oflSce, to wrest from 

 Nature the secrets of her magic. He it was who found out the 

 secret of the induction coil, and that if a copper disc be revolved 

 between the poles of a magnet a current of electricity is set up 

 without any other aid, — -a discovery which Dr. Fleming called 

 the " great-grandfather of all modern dynamo machines." In 

 1865, — an important year in the history of electricity, — 

 Clarke-Maxwell, a pupil of Faraday's, came first to the 

 definite conclusion that electrical eft'ects must be due to opera- 

 tions taking place in a medium filling all space, and that 

 these operations consisted of wave-like movements in this 

 medium, "ether," which were of a different order from 

 those which are appreciated by our senses as light. A very 

 beautiful illustration to explain the purely up-and-down vertical 

 motion of the substance of waves was thrown on the sheet. It 

 was now practically proved, said Dr. Fleming, that the medium 

 whose existence we had to assume to explain the phenomena of 

 light, and that which we assumed to explain electricity, was one 

 and the same. 



