Mr. J. P. Gassiot on Experiments made with RuhmkorfF's Coil. 97 



the voltaic current will pass simultaneously from the first to the 

 last plate of each group, through the intermediate plates and 

 fluid, and produce decomposition in each cell. This arrangement 

 is intended for a battery of 60 cells, in which each zinc plate is 

 6 inches by 4, all acting in one series. The intensity of the 

 current from this battery mil be reduced to that of 5 cells by 

 passing through the 12 decomposing cells. Each group of 13 

 plates will be covered with linen, which will prevent all foam, 

 because in each group the quantity of the gases will be only equal 

 to that which would be produced by 5 cells, or by j^th of 60. 

 January 25, 1854. 



XIII. On some Experiments made loith Ruhmkorff's Induction 

 Coil. By John P. Gassiot, Esq., F.R.S. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



ON the 7th of January, 1852, Mr. Grove communicated a 

 paper to the Royal Society (Phil. Trans. 1852, part 1) 

 entitled "On the Polarity of the Gases;" the experiments de- 

 scribed in this paper were made by him with a secondary coil appa- 

 ratus made by M. RuhmkorfF. Mr. Grove, who in his paper fully 

 describes its construction, kindly procured a similar instrument 

 for me, and a short time since I obtained another from this 

 celebrated mechanician of Paris. This last is of the same dia- 

 meter, but nearly twice the length of the former coil ; and there 

 is a commutator attached to the primary coil by which the direc- 

 tion of the cm'reut can be instantly reversed. Three cells of 

 Grove's nitric acid battery are sufficient to excite the action. 



AVith this apparatus the transverse non-luminous or dark 

 bands first pointed out by IMr. Grove in the above paper, and 

 more particularly explained by him in a note dated June 9, 1852, 

 published in the Philosophical Magazine of that year, are obtained 

 in a very distinct manner. It is impossible to describe the 

 beauty of this experiment ; it must be seen to be appreciated ; 

 but those experiments I am about to mention will explain the 

 power of the instrument and the nature of the investigations to 

 which it is a]jplicable. It opens out a variety of new ideas as to 

 the extraordinary action or nature of induced currents, and as 

 such may probably not be uninteresting to the readers of the 

 Philosophical Magazine. 



I may explain that the end or terminals of the secondary coil, 

 as described by Mr. Grove in his paper, are supported by two 

 small glass ])illars; to these can be attached by binding-screws, 

 wires of any required length to form the connexion with the 

 apparatus necessary to be used in the following exj)eriments : — 



1. If the ends of the connecting wires are brought within 0'5 

 of an inch of each other, a discharge takes place through the air. 



