It is not
difficult to understand why this happens; each of the particles
becomes polarized by induction, and they then cling together end to
end, just like iron filings near a magnet. A feeble charge is often
sufficient to start this coagulating action. And when the particles
have grown into big ones, they easily and quickly fall. A stronger
charge forcibly drives them on to all electrified surfaces, where they
cling. A fine water fog in a bell jar, electrified, turns first into a
coarse fog or Scotch mist, and then into rain. Smoke also has its
particles coagulated, and a space can thus be cleared of it. I will
illustrate this action by making some artificial fogs in a bell-jar
furnished with a metal point. First burn some magnesium wire,
electrify it by a few turns of this small Voss machine, and the smoke
has become snow; the particles are elongated, and by pointing to the
charged rod indicate the lines of electrostatic force very
beautifully; electrify further, and the air is perfectly clear. Next
burn turpentine, and electrify gently; the dense black smoke
coagulates into black masses over an inch long; electrify further, and
the glass is covered with soot, but the air is clear.
Pages:
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68