206 
MESSRS. W. SPOTTISWOODE AND J. FLETCHER MOULTON 
fore in structure, with the blue haze at the back of ordinary striae, and it is a luminosity 
formed at the places where the non-luminous electric streams arrive at the surface of the 
stria, or where, as perhaps it should be stated, the positive currents that arrive meet 
the negative electricity set free by the pulse of positive electricity that has just been 
expelled from the stria. Now if we suppose that these discharges are effected by or 
accompanied by convection of free electricity on particles of gas, it does not seem 
impossible that a positively charged particle might pass so near a negatively charged 
particle that they would rotate rapidly round one another, under the influence of the 
mutual attraction of the free electricity with which they are respectively charged, thus 
forming an analogue to a circular current, which would behave like a magnetic particle 
just as the electrically laden particles in Crookes’ lines behave like flexible currents. 
In this way we should have matter capable of mutual attraction, it being assumed that 
there is on the average some directing force or factor which prevents the directions of 
the poles of the magnetic matter being completely indifferent. That in some way there 
must be manufactured out of the gas a substance capable of mutual attraction, which 
when formed into the glow has a surface tension, is quite evident from Mr. Crookes’ 
experiments with the radiometer, in which he found that the particles driven off the 
vanes (when used as a negative terminal) did not produce rotation so long as the glow 
did not intersect the side of the glass vessel. This is explicable only by supposing that 
the glow and the vane formed a physically continuous surface kept together by mutual 
forces. 
It may be objected to this theory that the circular currents produced by the 
two elements of a revolving pair would be in opposite directions, and that they would 
consequently represent two magnets having opposite polarity, which would neutralize 
one another. But there is no reason to think that the two currents would be always 
exactly equal; and any inequality in the currents would produce a preponderance of 
magnetic polarity, and the preceding remarks would apply. 
It is no objection to this theory that the bright portion of the glow does not appear 
magnetic. Its position is fixed by its being the locus of the extremities of the Crookes’ 
lines that proceed from the fixed negative terminal, and it can only be affected by the 
displacement or deformation of these lines, as is found to be the case. 
X.— The 'passage of the discharge through the tube occupies a time which is sufficiently 
small in comparison with the interred between the discharges to prevent any 
interference between successive electrical pulses. 
We shall now revert to the phenomena of the sensitive discharge, and show that 
all the effects of which we have spoken are due to actions whose durations are 
comprised within the time that a single pulse takes in passing through the tube, 
so that these effects are not in any way due to the action of one electrical pulse 
on a consecutive one. In other words, the whole of the effects take place in each 
