f an inch: A, B inductric positive,
discharge nearly all at _o_ by negative spark: A, B inductric negative,
discharge nearly all at _n_ by negative spark. Intervals = 0.8 of an inch,
and A, B inductric positive, discharge mostly at _o_ by negative brush: A,
B inductric negative, discharge all at _n_ by negative brush. Here the
negative discharge most facile.

1516. _Carbonic acid gas._--_n_ and _o_ = 0.1 of an inch: A, B inductric
positive, discharge nearly all at _o_, or negative: A, B inductric
negative, discharge nearly all at _n_, or negative. Intervals = 0.8 of an
inch: A, B inductric positive, discharge mostly at _o_, or negative. A, B
inductric negative, discharge all at _n_, or negative. In this case the
negative had a decided advantage in facility of discharge.

1517. Thus, if we may trust this form of experiment, the negative small
ball has a decided advantage in facilitating disruptive discharge over the
positive small ball in some gases, as in carbonic acid gas and coal gas
(1399.), whilst in others that conclusion seems more doubtful; and in
others, again, there seems a probability that the positive small ball may
be superior. All these results were obtained at very nearly the same
pressure of the atmosphere.

* * * * *

1518. I made some experiments in these gases whilst in the air jar (fig.
131.), as to the change from spark to brush, analogous to those in the open
air already described (1486. 1487.). I will give, in a Table, the results
as to when brush began to appear mingled with the spark; but the after
results were so varied, and the nature of the discharge in different gases
so different, that to insert the results obtained without further
investigation, would be of little use. At intervals less than those
expressed the discharge was always by spark.

_______________________________________________________________________
| | | |
| | Discharge between | Discharge between |
| | balls B and D. | balls A and C. |
| |___________________________|___________________________|
| | | | | |
| | Small ball | Small ball | Large ball | Large ball |
| | B inductric | B inductric | A inductric | A inductric |
| | _pos_. |