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.

The same year he was awarded the Royal Medal of the Royal Society
for his explanation of binocular vision, a research which led him to
construct the stereoscope. He showed that our impression of solidity
is gained by the combination in the mind of two separate pictures of an
object taken by both of our eyes from different points of view. Thus, in
the stereoscope, an arrangement of lenses and mirrors, two photographs
of the same object taken from different points are so combined as
to make the object stand out with a solid aspect. Sir David Brewster
improved the stereoscope by dispensing with the mirrors, and bringing it
into its existing form.

The 'pseudoscope' (Wheatstone was partial to exotic forms of speech) was
introduced by its professor in 1850, and is in some sort the reverse of
the stereoscope, since it causes a solid object to seem hollow, and a
nearer one to be farther off; thus, a bust appears to be a mask, and a
tree growing outside of a window looks as if it were growing inside the
room.

On November 26, 1840, he exhibited his electro-magnetic clock in the
library of the Royal Society, and propounded a plan for distributing the
correct time from a standard clock to a number of local timepieces.
The circuits of these were to be electrified by a key or contact-maker
actuated by the arbour of the standard, and their hands corrected by
electro-magnetism. The following January Alexander Bain took out a
patent for an electro-magnetic clock, and he subsequently charged
Wheatstone with appropriating his ideas. It appears that Bain worked as
a mechanist to Wheatstone from August to December, 1840, and he asserted
that he had communicated the idea of an electric clock to Wheatstone
during that period; but Wheatstone maintained that he had experimented
in that direction