et, the latter of whom sent him to Wheatstone.

At a second interview, Mr. Cooke told Wheatstone of his intention to
bring out a working telegraph, and explained his method. Wheatstone,
according to his own statement, remarked to Cooke that the method would
not act, and produced his own experimental telegraph. Finally, Cooke
proposed that they should enter into a partnership, but Wheatstone was
at first reluctant to comply. He was a well-known man of science, and
had meant to publish his results without seeking to make capital of
them. Cooke, on the other hand, declared that his sole object was to
make a fortune from the scheme. In May they agreed to join their forces,
Wheatstone contributing the scientific, and Cooke the administrative
talent. The deed of partnership was dated November 19, 1837. A joint
patent was taken out for their inventions, including the five-needle
telegraph of Wheatstone, and an alarm worked by a relay, in which the
current, by dipping a needle into mercury, completed a local circuit,
and released the detent of a clockwork.

The five-needle telegraph, which was mainly, if not entirely, due to
Wheatstone, was similar to that of Schilling, and based on the principle
enunciated by Ampere--that is to say, the current was sent into the line
by completing the circuit of the battery with a make and break key, and
at the other end it passed through a coil of wire surrounding a magnetic
needle free to turn round its centre. According as one pole of the
battery or the other was applied to the line by means of the key, the
current deflected the needle to one side or the other. There were five
separate circuits actuating five different needles. The latter were
pivoted in rows across the middle of a dial shaped like a diamond, and
having the letters of the alphabet arranged upon it in such a way that
a letter was literally pointed out by the current deflecting two of the
needles towards it.

An experimental line, with a sixth return wire, was run between the
Euston terminus and Camden Town station of the London and North Western
Railway on July 25, 1837. The actual distance was only one and a half
mile, but spare wire had been inserted in the circuit to increase its
length. It was late in the evening before the trial took place. Mr.
Cooke was in charge at Camden Town, while Mr. Robert Stephenson and
other gentlemen looked on; and Wheatstone sat at his instrument in a
dingy little room, lit by a tallow cand