ON ELECTRICAL DISCHARGES THROUGH RAREFIED GASES. 
189 
effects. But such is not the case. From the commencement to the end the special 
effects are wholly dissimilar to the relief-effects, showing clearly that the special effects 
cannot be due to an alteration in intensity of the same kind of electrical pulses that 
produce the relief-effects, but must be due to pulses of an opposite character. 
This is, of course, not the only proof that the electrical pulses that produce the two 
effects are of opposite kinds. In fact, an examination of the appearances of the two 
effects is almost enough to convince the observer that it is impossible that one can 
be a mere heightening of the other, so radical is the dissimilarity, especially in 
their more marked forms. But the proof given above is the simplest and most 
direct experimental proof, and it is sufficient at the present stage, even when taken 
alone. It will, however, be subsequently found that there is strong confirmation of 
the correctness of this view. 
We conclude, therefore, that the displacements of electricity in the tinfoil caused 
by joining it with the air-spark terminal are the same in period but opposite in 
character to those which produce the relief-effect. But it is evident, taking the 
positive terminal to be the air-spark terminal, that the former consist of periodic 
pulsations of positive electricity at the moments when the air-spark passes/'" Hence 
in the case of the non-relief-effect, the tinfoil receives a pulse of positive electricity 
each time a spark passes. This must be, as we have seen, of the opposite character 
to that which causes the relief-effect. Hence to every pulsation coming from the air- 
spark there corresponds in the case of the relief-effect a pulsation of negative 
electricity to the tinfoil; that is to say, a pulsation of positive electricity from the 
tinfoil. 
This conclusion is exactly what we might have expected on the assumption that 
when the positive is the air-spark terminal the positive electricity passes intermit¬ 
tently through the tube in pulses of the same period as the air-spark. If each time 
the air-spark passed there were a sudden charging-up of the positive terminal and the 
portion of the circuit metallically connected therewith, causing a sudden discharge of 
positive electricity into and through the tube, this positive electricity, on reaching 
the part near to the tinfoil, would, by its induction, tend to drive awmy positive 
electricity from the tinfoil, and to attract negative electricity to it. This is what 
we find to be the case, and similar reasoning will apply to the case when the negative 
is the air-spark terminal. Therefore we shall assume that in the relief-effect there 
is a pulse from the tinfoil of the same character as the excess of electricity within 
the part of the tube opposite to it, or as it may be more simply stated, a pulse of 
electricity to the tinfoil of the opposite character to the electricity which is discharged 
from the air-spark terminal; and that in the non-relief-effect there is a pulse to the 
tinfoil of the same kind as the electricity which is discharged from that terminal. 
* If it is necessary to give an experimental proof for a conclusion so obvious, it is sufficient to connect 
tbis portion of the circuit to earth, placing a telephone in circuit, when the air-spark note will distinctly 
be heard, showing that there are periodic variations of potential accompanying each spark. 
