"influence" machines for generating electricity. Perhaps the most
effective of these is the Wimshurst, which we illustrate in figure
10, where PP are two circular glass plates which rotate in
opposite directions on turning the handle. On the outer rim of
each is cemented a row of radial slips of metal at equal
intervals. The slips at opposite ends of a diameter are connected
together twice during each revolution of the plates by wire
brushes S, and collecting combs TT serve to charge the positive
and negative conductors CC, which yield very powerful sparks at
the knobs K above. The given theory of this machine may be open to
question, but there can be no doubt of its wonderful performance.
A small one produces a violent spark 8 or 10 inches long after a
few turns of the handle.

The electricity of friction is so unmanageable that it has not
been applied in practice to any great extent. In 1753 Mr. Charles
Morrison, of Greenock, published the first plan of an electric
telegraph in the Scots Magazine, and proposed to charge an
insulated wire at the near end so as to make it attract printed
letters of the alphabet at the far end. Sir Francis Ronalds also
invented a telegraph actuated by this kind of electricity, but
neither of these came into use. Morrison, an obscure genius, was
before his age, and Ronalds was politely informed by the
Government of his day that "telegraphs of any kind were wholly
unnecessary." Little instruments for lighting gas by means of the
spark are, however, made, and the noxious fumes of chemical and
lead works are condensed and laid by the discharge from the
Wimshurst machine. The electricity shed in the air causes the dust
and smoke to adhere by induction and settle in flakes upon the
sides of the flues. Perhaps the old remark that "smuts" or