336 On a new Instrument for Registering Electrical Discharges. 



operation, I connected with the conductor a jar containing a 

 square foot of surface, in communication with which were a 

 Lane's discharger, the spark-counter, andathermo-electrometer. 

 The discharging interval was adjusted so that each discharge 

 produced one degree of effect upon the thermo-electi-ometer. 

 This interval was rather more than 0'2 of an inch, and the dis- 

 charges passed at the rate of seven per second. The discharger 

 was fitted with balls of 1 inch diameter, and the bottom of the 

 jar was connected with the gas-fittings. The total rise of the 

 thermo-electrometer was 20 degrees. 



On comparing these effects with those of the coil, it would 

 appear that since the latter is capable of producing from 100 to 

 150 discharges per second, or even more, each raising the fluid 

 1 degree of the thermo-electrometer, it would be equivalent to 

 fifteen or twenty such hydro-electi'ic machines. I next discon- 

 nected the jar and caused a current of dense sparks of 2 inches 

 in length to pass from the conductor through the spark-counter 

 and thermo-electrometer, the latter being in connexion with the 

 gas-fittings, and with this arrangement 1 obtained sparks at the 

 rate of thirteen per second, producing a rise in the thermometer 

 of only 5 degrees. I had the curiosity to receive a few of these 

 sparks on my hand; they were extremely violent, and were felt 

 very powerfully in the legs and heels, although the floor was 

 wood. They were not, however, so painful as static sparks from 

 the outer terminal of the coil. 



The quantity of electricity developed by this hydro-electric 

 machine must have been very great, since on attempting to re- 

 duce the rapidity of the discharges of the jar by placing an im- 

 perfect conductor in contact with the machine, I found that my 

 oak walking-stick produced scarcely any effect when laid upon 

 the conductor, until the portion between the conductor and my 

 hand was reduced to 3 or 4 inches. 



The quantity of static electricity developed by the coil appears 

 by these comparisons to be very great, but its effects are of a very 

 peculiar kind. One cannot help being struck with the difference 

 between the character of the current which excites the machine 

 and that developed by it. The former possesses no tension, but 

 great thermal and magnetic power; the latter great tension, and, 

 if unassisted by the jar, no thermal power in a metallic circuit, 

 except at the discharging ends ; and here, as I have before stated, 

 it is doubtful whether the heat is elicited from the intervening 

 medium or the metal itself. The thermal effect, however, pro- 

 duced by the jar opens a curious inquiry as to the extent to 

 which it might be increased by increasing the size of the coil. I 

 have hitherto only produced, by the induced current and the 

 jar, the ignition of 4 or 5 inches of fine platina wire ; whereas 



