240 Mr. C. F. Varley on the Discharge of Electricity [Jan. 12, 



these particles seem to be thrown by momentum on each side of the nega- 

 tive pole, beyond the limit of the electric current. 



This arch requires time for its formation, for when a charged condenser 

 is discharged through the tube no arch is produced. The arch from the 

 negative pole is a hollow cylinder ; the little talc tell-tale against which 

 the arch was projected cut out the light, and a corresponding dark space 

 existed throughout the remainder of the course of the arch. 



There was on the talc, at the spot where the arch struck it, a little bright 

 luminous cloud, as though the attenuated luminous vapour were condensed 

 by this material obstruction. 



Great care had been taken not to let the arch strike the single filament 

 of silk which suspended the talc. Having demonstrated that the talc was 

 repelled as described, the arch was allowed to play against the silk fibre, 

 which the author expected would have been instantly burnt ; such, however, 

 was not the case. Even when a powerful induction-coil replaced the battery, 

 the fibre remained unhurt. 



Comparison of the above Phenomena with Discharges between the Poles of 

 a Holtz's Machine in air. 



In the first part of this paper four different kinds of discharges were de- 

 scribed in vacuo. With a "Holtz's" machine, which will give 1 1-inch sparks 

 in the air, four well-marked different kinds of discharge have been ob- 

 tained in the air ; one of which, the author thinks, will explain the curious 

 and rare phenomenon known as " ball lightning." 



In the experiments hereafter referred to, the condensers were in all cases 

 attached to the " Holtz's " machine. The first discharge is the long 1 1-inch 

 zigzag spark or lightning-flash ; the second is the well-known "brush," 

 which is best obtained by connecting the negative pole of the "Holtz's" 

 machine to the earth ; the third kind of discharge is a hissing red flame, 

 g inch in length, playing about the negative pole, the positive pole being 

 scarcely luminous at all, and if luminous, at one or two points only ; the 

 fourth or most remarkable phenomenon is best obtained in the following 

 manner (it should be understood that the brass balls on each of the poles are 

 about an inch in diameter) : — Tie to the negative pole a small thin strip or 

 filament of wood, 3 inches in length, and bent so as to project on each side 

 of the negative pole, and a little beyond it towards the positive. On 

 rotating the machine, two bright spots are seen upon the positive pole. If 

 the positive pole be made to rotate upon its axis, the luminous spots do not 

 rotate with it ; if, however, the negative pole, with its filament of wood, be 

 rotated, the spots on the positive pole obey it, and rotate also. The in- 

 sertion of a non-conductor, such as a strip of glass, in front of the pro- 

 jecting wooden end, obliterates the luminous spot on the positive pole. 

 When the author first discovered this, he, seeing apparently pieces of dirt 

 on the positive pole, wiped it clean with a silk handkerchief, but there 



