340 
MR. T. ROYDS ON THE CONSTITUTION OF THE ELECTRIC SPARK. 
have a smaller inclination than the first. The streamers of the lead lines are seen to 
be shortened and the velocity is smaller. 
In Table I. are given the average velocities in metres per second (Y) of the various 
metals in the order of their atomic weights. The lines of type I. are those whose 
streamers form into an envelope, and type II. comprises the short lines which have a 
high velocity indicated by the first streamer only. 
Table I.—Velocities. 
Metal. 
Lines. 
Type of 
line. 
Y met./sec. 
p(H = l). 
V 2 p/(64 f. 
Magnesium . 
4481 
I. 
460 
12 
624 
Aluminium . 
4530, 4521, 4479 
II. 
1 870 
13-5 
2,520 
Calcium 
3969, 3934, 3737, 3706 
I. 
416 
20 
850 
Zinc 
4925, 4912 
I. 
388 
33 
1,200 
Cadmium . 
4416 
I. 
404 
56 
2,240 
Tin .... 
4586, 4216, 3908, 3861, 3745 
11. 
1 1370 
60 
27,400 
Antimony 
4693, 4592, 4352, 4265 
II. 
1 2230 
60 
80,000 
f 4358, 4047 
936 
100 
21,500 
Mercury . . < 
3984 , 
4358, 4047 1 from Cd amalgam 
1155 
532 
32,700 
3984 J (78 per cent. Hg) 
633 
Lead . . . < 
' 4387, 4245 
I. 
303 
103 
2,325 
4798, 4761, 3854 
II. 
1960 
98,000 
Bismuth . . « 
f 4302, 4260, 4079, 3864, 3793 
I. 
283 
104 
2,045 
[ 4798, 4751, 4561, 3696, 3614 
II. 
2024 
104,500 
The effect of electric intensity on the velocity of the metallic vapour has been 
investigated by varying the capacity. A discharging key was introduced into the 
circuit and the spark made to pass by pressing the key when the Wimshurst had 
been rotated a certain number of times. In this way only the spark voltage was 
altered. The results are given in Table II. for different spark lengths. Whilst the 
variation of velocity is slight, the tendency is that the velocity increases with 
diminishing capacity, i.e., with increasing voltage. Schuster and Hemsalech found 
the same tendency. 
Table II.—Effect of Capacity on the Velocity. 
Bismuth. 
Length of gap. 
Capacity = 0-0306 mfd. 
= 0-0206 mfd. 
= 0-0103 mfd. 
centims. 
0-5 
Y = 295 
= 340 
— 
0-8 
283 
316 
= 1 457 
1-2 
317 
1 496 
332 
