APPENDIX I. clvii 



compare them, in the manner stated in a preceding paragraph, with 

 his own previous deductions from the testings of the Atlantic cable 

 during its manufacture in 1857, and with Weber's measurements of 

 the specific resistance of copper.' It has now become universally 

 adopted first of all in England ; twenty-two years later by Germany, 

 the country of its birth ; and by France and Italy, and all the other 

 countries of Europe and America practically the whole scientific 

 world at the Electrical Congress in Paris in the years 1882 and 

 1884. 



An important paper of thirty quarto pages published in the 

 ' Transactions of the Royal Society ' for June 19, 1862, under the 

 title ' Experimental Researches on the Transmission of Electric 

 Signals through submarine cables, Part I. Laws of Transmission 

 through various lengths of one cable, by Fleeming Jenkin, Esq., 

 communicated by C. Wheatstone, Esq., F.R.S.,' contains an account 

 of a large part of Jenkin's experimental work in the Birkenhead 

 factory during the years 1859 and 1860. This paper is called Part I. 

 Part II. alas never appeared, but something that it would have 

 included we can see from the following ominous statement which I 

 find near the end of Part I. ' From this value, the electrostatical 

 capacity per unit of length and the specific inductive capacity 

 of the dielectric, could be determined. These points will, how- 

 ever, be more fully treated of in the second part of this paper.' 

 Jenkin had in fact made a determination at Birkenhead of the 

 specific inductive capacity o gutta-percha, or of the gutta-percha 

 and Chatterton's compound constituting the insulation of the cable, 

 on which he experimented. This was the very first true measure- 

 ment of the specific inductive capacity of a dielectric which had 

 been made after the discovery by Faraday of the existence of the 

 property, and his primitive measurement of it for the three sub- 

 stances, glass, shellac, and sulphur ; and at the time when Jenkin 

 made his measurements the existence of specific inductive capacity 

 was either unknown, or ignored, or denied, by almost all the scientific 

 authorities of the day. 



The original determination of the microfarad, brought out under 

 the auspices of the British Association Committee on Electrical 

 Standards, is due to experimental work by Jenkin, described in a 

 paper, ' Experiments on Capacity/ constituting No. IY. of the ap- 

 pendix to the Report presented by the Committee to the Dundee 

 Meeting of 1867. No other determination, so far as I know, of this 

 important element of electric measurement has hitherto been made ; 



k2 



