xxvi INTRODUCTORY 



mirror instrument while listening to the loud ticking of the 

 seconds of a clock specially made for astronomical work. 

 The signal had to be sent from one end and recorded at 

 the other at the exact tick, and Mr. Finlay showed me the 

 importance of determining my personal coefficient of 

 error in reading in order that allowance might be made 

 for it. 



Some time afterwards, while engaged in cable-testing 

 at Delagoa Bay, I noticed a deflection upon the scale of 

 the Astatic reflecting galvanometer for which I could not 

 account, and upon investigation found the disturbing 

 influence to proceed from my own body. This led to a 

 series of experiments which convinced me that a force 

 resembling electricity, if not identical with it, was con- 

 stantly generated in the body, and that its tension was 

 dependent upon the state of health of the subject. 



Some few years later I was invalided home, and at the 

 instance of Sir James Anderson and Sir John Fender to 

 whom the journal then belonged was associated in the 

 editorship of The Electrician, and also became editor of 

 The Electrical Engineer. In the latter paper, in May, 

 1885, I published an article entitled " The Human Body 

 as a Disturbing Element in Electrical Testing," from which 

 the following quotation may be made : 



" I am of opinion that in every case where use is made 

 of an unshunted galvanometer of great sensibility the 

 operator should be careful to connect himself during the 

 test with an earth plate, instead of, as is usual, standing 

 upon some insulating substance. This conclusion was 

 forced upon me years ago. I was, in the ordinary course 

 of business, comparinga 10-microfarad condenser with one of 

 1-micro capacity by Sir William Thomson's " (afterwards 



