ON ELECTRICAL DISCHARGES THROUGH RAREFIED GASES. 
205 
segments of the discharge; and hence it is not to be wondered at that we should find 
that the distance across which the non-luminous discharge takes place in these 
segments is not identical with that which prevails in the other segments, all of which 
resemble each other so closely in these respects. And though we would not adduce 
any considerations as to what is more or less probable, unsupported by experiment, 
yet we are, we think, justified in saying that it is just in such respects that we should 
expect to find the details of a unit of striated discharge modified by changes in its 
terminal arrangements. 
It will be seen that the authors of this paper regard each segment as constituting a 
separate discharge. One phenomenon observed by them, of a different kind to those 
of which we have been chiefly speaking, appears strongly to confirm this. If a magnet 
be applied to a striated column, it will be found that the column is not simply thrown 
up or down as a whole, as would be the case if the discharge passed in direct lines from 
terminal to terminal, threading the striae in its passage. On the contrary, each stria 
is subjected to a rotation or deformation of exactly the same character as would be 
caused if the stria marked the termination of flexible currents radiating' from the 
bright head of the stria behind it and terminating in the hazy inner surface of the 
stria in question. An examination of several cases has led the authors of this paper 
to conclude that the currents do thus radiate from the bright head of a stria to the 
inner surface of the next, and that there is no direct passage from one terminal of the 
tube to the other. 
It is natural to inquire what, in this theory, is the physical structure of strise. Are 
they merely luminous appearances (i.e., loci of maximum luminosity), or are they 
aggregations of matter having a material structure ? This is a question which it is 
beyond the scope of this paper to discuss, but the most probable view, in the opinion 
of the authors, is that they should be regarded as septa of complete electric porosity, 
having a material structure. One of the most important facts favouring this conclu¬ 
sion is that when strise are formed by a coil working with a high-speed break, the 
strife produced by the two currents (the make and the break) adhere persistently 
together in pairs as though the alternate currents found ready to hand striae that only 
needed a little deformation to make them available for their purposes (Plate 17, fig. 15). 
There are other facts tending to support this conclusion, but a complete examination 
of the question would carry us beyond the limits of the present paper. 
A great difficulty in the way of this, and indeed of all attempted solutions of the 
stratification of vacuum discharges, arises from the difficulty of imagining any physical 
cause which could form material aggregations in the form of strise out of the diffused 
and mutually repellant particles of the rarefied gas. The following theory is thrown 
out as a suggestion of a possible mode of accounting for their formation. It is known 
that the blue haze that surrounds the negative halo or glow is magnetic, and follows 
the lines of magnetic force just as would be the case were it a mass of magnetized 
steel filings. Now on the present theory this haze is identical in function, and there- 
