682 ALEXANDER MACFARLANE AND P. M. PLAYFAIR ON THE 
as to be in planes at right angles to one another and to the brass plate. 

Fig. 1. 
TaBLE III.—Single Sparks between Platinum Wires, 21st June 1878. 
Shortest distance between wires, 4 mm. 

Lower Wire, Nega- 
tive and Heated 
Lower Wire, Posi- 
tive and Heated 
allowed longer 
time to cool 
Upper Wire, Posi- 
tive and Heated 
9 
»” 


















The shortest distance between the wires is 4mm. | 
The figure represents the apparatus suspended 
by means of the upper wire from one conductor 
of the Holtz machine, and the lower wire con- 
nected with the positive conductor. Only the 
wire which was not at the time bearing the weight 
could be heated without introducing an alteration 
of the distance between the wires. The heating — 
was effected by bringing the terminals ofa battery _ 
of four Bunsen elements, arranged in multiple 
arc, into contact with the platinum wire, at a dis- 
tance of an inch apart. The following series of 
observations is representative of all made :— 
Deflection. Zero. Difference. Mean. 
nN. Nl. 
Before heating, 340 463 123 
x; 338 462 ia} 124°3 
5 335 461 126 
Heated, . 335 460 125) 
ss 305 462 127 | 
- 335 460 125 | 
ba 345 3 115 > 122'3 
345 - 115 
335 459 124 
~ 335 460 125 J rs 
Before heating, 335 460 125 125 4 
A: 335 a 125 i 
Heated, . 385 - 75 * 
: 365 é 95 a 
L 355 . 105 4 
> 368 : 92 s. 
. 349 iG 111 93:3 
: 385 (6 Z| 
»” 385 ” 75 | 3 ¥ 
is 355 105 P 
§ 353 Fe 107 J ; a 
es 370 e 90 ; oa 
3 355 % 105 100 § | 
; 355 ‘ 105 J : | 
a. 
! 
Before heating, 345 460 115 \ 

