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Between the poles of the galvanometer was stretched
a slender thread of fused quartz plated with silver, only one one-
thousandth of a millimetre in diameter, so tenuous that it could
not be seen except in a bright light. It was a thread so slender
that it might have been spun by a miscroscopic spider.
Three feet farther away was a camera with a moving film of
sensitised material, the turning of which was regulated by a
little flywheel. The beam of light focused on the thread in the
galvanometer passed to the photographic film, intercepted only by
the five spindles of the wheel, which turned once a second, thus
marking the picture off into exact fifths of a second. The
vibrations of the microscopic quartz thread were enormously
magnified on the sensitive film by a lens and resulted in
producing a long zig-zag, wavy line. The whole was shielded by a
wooden hood which permitted no light, except the slender ray, to
strike it. The film revolved slowly across the field, its speed
regulated by the flywheel, and all moved by an electric motor.


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