ELECTRIC DISCHARGES IN GASES AT LOW PRESSURES. 
413 
Table III.—Hydrogen. 
Spark length 
= 1 millim. 
Spark length 
= 2 millims. 
Spark length 
= 3 millims. 
Spark length 
= 5 millims. 
Spark length 
= 10 millims. 
Pressures 
ill 
Spark 
Pressures 
Spark 
Pressures 
in 
millims. 
Spark 
Pressures 
Spark 
Pressures 
Spark 
millims. 
potential 
millims. 
potential 
potential 
millims. 
potential 
in 
millims. 
potential 
of 
mercury. 
in 
volts. 
of 
mercxiry. 
in 
volts. 
of 
mercury. 
m 
volts. 
of 
mercury. 
in 
volts. 
of 
mercury. 
in 
volts. 
21-7 
328 
23 
435 
13-6 
415 
13-6 
469 
7-58 
526 
16-2 
300 
14-8 
360 
8-54 
356 
9-35 
415 
4-37 
427 
11-9 
281 
IDO 
323 
5-40 
301 
6-02 
350 
2-55 
335 
10-3 
278 
8-08 
299 
4-66 
286 
3-80 
300 
D77 
299 
8-94 
287 
6-95 
285 
4-02 
278 
3-28 
287 
1-46 
283 
7-74 
306 
5-93 
279 
3-44 
282 
2-80 
281 
1 • 22 
287 
6-52 
335 
5‘04 
284 
2-93 
292 
2-41 
282 
DOl 
295 
5-57 
374 
4-30 
293 
2-52 
310 
2-05 
285 
•846 
313 
4-73 
487 
3-72 
305 
2-15 
356 
D76 
293 
•700 
343 
4-11 
649 
3-23 
333 
D85 
440 
D51 
305 
•575 
426 
3-.54 
905 
2-77 
399 
D59 
564 
1 -26 
345 
•470 
595 
3-04 
1275 
2-36 
523 
1 - .35 
780 
1 -09 
410 
•390 
8.50 
2-60 
1781 
2-03 
727 
1 -16 
1054 
•928 
539 
•330 
1142 ' 
— 
— 
D73 
1010 
DOO 
1382 
•808 
706 
•276 
1477 
— 
— 
D48 
1380 
•861 
1789 
•700 
975 
•264 
1710 
— 
— 
D33 
1746 
— 
— 
•600 
1373 
_ 
; 
— 
•516 
1775 
— 
— 
Ill the experiments with this gas, readings were taken for the same electrode 
distances I, 2, 3, 5 and 10 miUims., and the values of the spark potentials and their 
corresponding pressures are given in Table III. These numbers are also graphically 
set forth in fig. 4. 
We see from this table that the readings corresponding to the spark potential 
1800 volts are : 
Distance between electrodes 
in millims. 
1 
2 
3 
5 
10 
Discharge pressures in millims. 
of mercury. 
2-60 
1-33 
•861 
•516 
•264 
which pressures are in the ratio 9-9 : 5-0 : 3-2 : 2-0 : 1. 
Again, with a spark potential of 500 volts the readings give : 
