HISTORY AND PROGRESS. 11 



invention of Mr. Ronalds, of Hammersmith. For the pur- 

 poses of experiment he erected a line, eight miles long, 

 insulated by silk and dry wood, in his garden, and also 

 buried a considerable length of wire, insulated in glass tubes, 

 encased in pitch and wood, in the earth. This was in 1823. 

 For the following description of the invention we are in- 

 debted to Mr. E. Highton's* book : 



Ronalds employed an ordinary electric machine and the 

 pith-ball electrometer in the following manner. He placed 

 two clocks at two stations ; these two clocks had upon the 

 second-hand arbour a dial with twenty letters on it ; a screen 

 was placed in front of each of these dials, and an orifice was 

 cut in each screen, so that one letter only at a time could be 

 seen on the revolving dial. The clocks were made to go 

 isochronously, and as the dials moved round, the same 

 letter always appeared through the orifices of each of these 

 screens. The pith-ball electrometers were hung in front of 

 the dials. 



It is evident, therefore, that if these pith balls could 

 be made to move at the same instant of time, a person at 

 the transmitting station, by causing such motion in both 

 those electrometers, would be able to inform the attendant 

 at the distant or receiving station what letters to note down 

 as they appeared before him in succession on the dial of the 

 clock. 



This was accomplished in the following manner. The 

 transmitter caused a current of electricity to be constantly 

 operating upon the electrometers, except only when it was 

 required to denote a letter, and then he discharged the 

 electricity from the wire, and instantly both balls collapsed. 

 The distant observer was thereby informed to note down the 

 letter then visible. In this way letter after letter could be 

 denoted, words spelt, and intelligence of any kind trans- 

 mitted. All that was absolutely required for this form of 

 telegraph was, that the clocks should go isochronously during 

 the time that intelligence was being transmitted ; for it was 

 easy enough by a preconcerted arrangement between the 

 * " The Electric Telegraph," by E. Highton, p. 50. 1852. 



