NEW EFFECTS OF INDUCED ELECTRICITY. 397 



dary coil of Ruhmkorff's apparatus, a great increase in the 

 brilliancy of the discharge could be obtained. Circumstances 

 diverted my attention from it at the time, and I did not pub- 

 lish the experiment, though I believe Mr. Gassiot mentioned 

 it in one of his papers. I have since heard that M. Sinsteden, 

 in France, had made the same observation, though I do not 

 know when, nor whether he has published his experiments. 



The point which I now think may be worth insertion in 

 the ' Phil. Mag.' is the conversion, by means of a Ruhmkorff 

 coil, of an indefinite amount of voltaic into static electricity. 

 If a small Leyden phial have its coatings connected respec- 

 tively with the extremities of the secondary wire of a Ruhm- 

 korfT coil (the primary being, as usual, connected with the 

 condenser of M. Fizeau, and two wires being attached to 

 the terminals and brought within striking distance), the 

 noise and brilliancy of the discharges are greatly increased, 

 with generally a slight diminution in their length. If 

 now the voltaic series be increased, the coil and Leyden 

 phial remaining the same, but little increase in the length or 

 brilliancy of the sparks will ensue, that is, provided the bat- 

 tery was in the first instance sufficiently powerful to give the 

 maximum effect of the coil without the phial. For instance, 

 if with a Ruhmkorff" coil of the size now usually made, ten 

 inches long by four diameter, four cells of two inches by four 

 of the nitric acid battery be used, and a pint Leyden phial, but 

 little increase of effect will be obtained by using eight or more 

 cells, and the platinum at the contact-breaker would be 

 rapidly destroyed by the sparks. 



But substitute for the pint Leyden phial one of double 

 the capacity, and it will be found that though this second 

 phial was inferior to the first with a battery of four cells (giv- 

 ing shorter sparks, and fewer in a given time, though some- 

 what denser), yet it is far superior to the first with the battery 

 of eight cells, and the sparks at the contact-breaker are no 

 longer injurious. 



By adding more coated surface, for instance, another phial, 

 four more cells may be added, and increased effects will be 

 obtained, and thus with the same coil the brilliancy of the dis- 

 charge may be increased to an extent to which I have not yet 

 found a limit. I obtained this result some months back ; but 



