' The decision,
however vague, pronounces the needle telegraph a joint production. If
it was mainly invented by Wheatstone, it was chiefly introduced by
Cooke. Their respective shares in the undertaking might be compared to
that of an author and his publisher, but for the fact that Cooke himself
had a share in the actual work of invention.
In 1840 Wheatstone had patented an alphabetical telegraph, or,
'Wheatstone A B C instrument,' which moved with a step-by-step motion,
and showed the letters of the message upon a dial. The same principle
was utilised in his type-printing telegraph, patented in 1841. This was
the first apparatus which printed a telegram in type. It was worked by
two circuits, and as the type revolved a hammer, actuated by the
current, pressed the required letter on the paper. in 1840 Wheatstone
also brought out his magneto-electrical machine for generating
continuous currents, and his chronoscope, for measuring minute intervals
of time, which was used in determining the speed of a bullet or the
passage of a star. In this apparatus an electric current actuated an
electro-magnet, which noted the instant of an occurrence by means of a
pencil on a moving paper. It is said to have been capable of
distinguishing 1/7300 part of a second, and the time a body took to fall
from a height of one inch.
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