METALLIC WIRES BY ELECTRICITY. 437 
Number Quantity of 
of jars. electricity. 
4 6 A spark on the inner side of the wire, on 
that side nearest to the inner surface 
of the battery. 
8 Streak of vapour the whole length of the 
wire. 
9 Vapour—spark on the outer side. 
10 The same. 
11 No spark or vapour—deep bend. 
12 Spark on the outer side—increased bend. 
13 The wire is red-hot. 
Experiment 3.—On a considerably thicker wire (radius 
0°04053) the following effects were observed :— 
Number Quantity of 
of jars. electricity. 
4 12 
14 Spark on the outer side. 
16 Spreading spark on the outer side. 
18 Bend in the wire. 
20 The same increased. 
22 Several bends. 
24 The same increased. 
5 26 The same. 
27, The wire is red-hot. 
28 The wire glows brightly — many deep 
bends. 
Long before the amount of electricity has been attained ne- 
cessary to produce a red heat, the effects observed on the wire 
prove that the electricity has penetrated it in a powerful manner. 
The wire is visibly shaken, small sparks appear at its ends, and 
particles are forcibly torn from its surface, which rise from it in 
the form of a dense vapour. It often happens that contemporary 
with the spark larger pieces of metal are thrown off, which being 
red-hot give a spreading appearance to the spark. These effects 
are never entirely wanting, but they are not constant in inten- 
sity. The vibrations are so much the more obvious as the wire 
is easily put in motion, and the size of the sparks at the ends 
depends upon the material of the wire, and upon the form and 
material of support. In the present instance, when the wire 
lay in rounded clamps of bell-metal, the sparks were powerful 
