THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[FOURTH SERIES.] 



MA Y 1867. 



XLIII. On one of Ohm's Laws relating to an Insulated Circuit. 

 By F. C. Webb, C.E.* 



MANY of the foruiulse given by Ohm are in constant use in 

 practical telegraphy, and have thus for years borne the 

 test of experiment. There are, however, some others which, 

 having at present apparently no practical bearing on telegraphy, 

 have not been so frequently tested, or, indeed, noticed, even if they 

 have ever before been subjected to experiment, except by Ohm 

 himself. 



The following experimental verification of a very peculiar pro- 

 perty of the galvanic circuit (certain conditions being fulfilled 

 which, it will be seen, should have been specfied by Ohm) may 

 perhaps be of interest to those who take an interest in the science 

 of electricity. 



The problem relates to the alteration in the distribution of the 

 tensions in an insulated closed galvanic circuit when one point 

 of the circuit is connected to an insulated conducting body, and 

 is thus stated in the translation given by Mr. W. Francis of 

 Ohm's paper f : — 



" Since each place of a galvanic circuit undergoes of itself the 

 same change to which a single place was compelled, the change 

 in the quantity of electricity, extending over the whole circuit, is 

 proportional, on the one hand, to the sum of all the places, i. e. 

 to the space over which the electricity is diffused in the circuit, 

 and, moreover, to the change in the electric force produced at one 

 of these places. From this simple law result the following di- 

 stinct phenomena. If we call r the space over which the electri- 



* Communicated by the Author. 

 t Taylor's Scientific Memoirs, Part VII. p. 418. 

 Phil Mag. S. 4. Vol. 33. No. 224. May 1867. Y 



