DISCHARGE OF ELECTRICITY FRUM GLOWING CARBON. 209 
The potential difference necessary to start arcing, however, 
depends very considerably on the position of the hot 
relatively to the cool carbon, and we give in table I] 
measurements of this quantity taken with the hot carbon 
vertically below, and with it vertically above, the cool 
positive; in the lower part of the table are given the 
values of the critical voltage with the hot carbon vertically 
below the cool one, and with it in the same horizontal 
plane as the other electrode. 
TABLE II. 
Distance Temperature. Critical voltage for arcing. 
between | Difference. 
carbons. | Hot carbon. | Cool carbon. | Hot carbon, | Hot carbon, 
| © ‘ a below. above. ta. 8 
3 nom. 1930°C.| 1420°C.| 56:0 volts 180 
” 9 346 | | 74:0 volts 
eau 121.10 D5 10UO 39500 
Ba cin 3 650 “BAS owe 
i 2230 1550 26-5 
: ¥ .860 39:0 Lene 
» | 2460 W620) 931 19'5 | ys 
i A 1240 | 20°5 
Imm. | 1930 1580 360 24 
f . 1280 | 440 
2 ” 9 1530 43-0 ; 
‘ ‘i 840 52-0 HOMO 
37), ‘ 1420 56-0 
' ; 346 74:0 Men 
Carbons in 
| same horizon- 
| 1930 1580 36:0 tal plane. + 
- : 1500 42:0 e 
Aas f 1530 | 42-0 re 
os 3 1200 46:0 
uae f 1420 56-0 ae 
33 ” 1000 59°5 
" 2230 1550 | 26-5 ae 
9 - 1240 29°5 
It is seen from the table that the potential difference 
required for arcing is less when the hot carbon is vertically 
N—Sept. 2, 1908. 
