224 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
the circumstances just described, it will be remembered that a nebulous discharge 
occurred in V without stratification, and that no illumination of the tell-tale tube 
took place. The battery was also connected at the S terminal, without any inter- 
vening resistance, to one side A A' of a condenser, the Z terminal to a key K ; when 
this was pressed down, then, and only then, the other side of the B B' condenser 
was connected with the battery, and it became charged. With the condenser in 
action strata were produced in Y, and the tell-tale tube V 2 was illuminated, showing 
that an induced current was produced in the secondary wire ; this we ascribed to a 
periodic overflow from the condenser, in addition to the current which was passing 
continuously from the battery. 
230. — One of the most beautiful examples of the difference of discharge, with _ 
and without the condenser, was presented in December, 1874, by tube 53, 
which is represented in fig. 67, half-size. The negative wire lies in the 
axis of the tube, and reaches to within 0‘25 inch of the positive terminal 
which enters the tube at right angles to it. On the negative wire are 
several glass beads or bugles, kept in place by expanding the wire in one 
direction by a slight blow with a hammer ; the resistance of the tube, which 
was charged with carbonic acid, was found to be 50,000 ohms. With 980 
powder cells, without the condenser, a beautiful tuft of violet light appeared 
on each of the spaces of uncovered wire, without the slightest indication 
of stratification, but on pressing down the key K in fig. 66, so as to connect 
the battery with a condenser of 0’5442 m.f. capacity, the tell-tale tube 
lighted up, and the discharge throughout tube 53 was stratified, as shown 
in fig. 67, the strata on the uncovered portions of the wire being violet, and 
those on the glass-covered part salmon coloured, and much fainter. 
Eig. 67. 
In order to produce these effects, we find that it is essential to use an induction 
coil, the primary of which presents very little resistance ; for example, Apps’s 815, the 
particulars of which are given in Part I., page 106, the resistance of the primary being 
only 0‘245 ohm. They cannot be obtained by using the induction coil 819, Part I., 
page 64, this offering too much resistance, 316 ohms. 
In order that the copies of the photographs in Plate 18, referring to the phenomena, 
may be understood, we insert fig. 68, which shows the disposition of the tube T T', 
