clvi MEMOIR 



the chief subject of our conversations and discussions ; as it was in 

 fact the practical object of Jenkin's visit to me in Glasgow ; but not 

 much of the week had passed before I found him remarkably inter- 

 ested in science generally, and full of intelligent eagerness on many 

 particular questions of dynamics and physics. When he returned 

 from Glasgow to Birkenhead a correspondence commenced between 

 us, which was continued without intermission up to the last days of 

 his life. It commenced with a well-sustained fire of letters on each 

 side about the physical qualities of submarine cables, and the prac- 

 tical results attainable in the way of rapid signalling through them. 

 Jenkin used excellently the valuable opportunities for experiment 

 allowed him by Newall, and his partner Lewis Gordon, at their 

 Birkenhead factory. Thus he began definite scientific investigation 

 of the copper resistance of the conductor, and the insulating resist- 

 ance and specific inductive capacity of its gutta-percha coating, in 

 the factory, in various stages of manufacture ; and he was the very 

 first to introduce systematically into practice the grand system of 

 absolute measurement founded in Germany by Gauss and Weber. 

 The immense value of this step, if only in respect to the electric 

 telegraph, is amply appreciated by all who remember or who have 

 read something of the history of submarine telegraphy ; but it can 

 scarcely be known generally how much it is due to Jenkin. 



Looking to the article ' Telegraph (Electric) ' in the last volume 

 of the old edition of the ' Encyclopaedia Britannica,' which was pub- 

 lished about the year 1861, we find on record that Jenkin's measure- 

 ments in absolute units of the specific resistance of pure gutta-percha, 

 and of the gutta-percha with Chatterton's compound constituting 

 the insulation of the Red Sea cable of 1859, are given as the only 

 results in the way of absolute measurements of the electric resistance 

 of an insulating material which had then been made. These remarks 

 are prefaced in the ' Encyclopaedia ' article by the following state- 

 ment : ' No telegraphic testing ought in future to be accepted in 

 any department of telegraphic business which has not this definite 

 character ; although it is only within the last year that convenient 

 instruments for working, in absolute measure, have been introduced 

 at all, and the whole system of absolute measure is still almost 

 unknown to practical electricians.' 



A particular result of great importance in respect to testing is 

 referred to as follows in the 'Encyclopaedia' article: 'The im- 

 portance of having results thus stated in absolute measure is illus- 

 trated by the circumstance, that the writer has been able at once to 



