and on which particular letters of the message were indicated by means of an electro-magnet and detent. Before the end of March he invented the clock-work alarm, in which an electro-magnet attracted an armature of soft iron, and thus withdrew a detent, allowing the works to strike the alarm. This idea was suggested to him on March 17, 1836, while reading Mrs. Mary Somerville's 'Connexion of the Physical Sciences,' in travelling from Heidelberg to Frankfort.
Cooke arrived in London on April 22, and wrote a pamphlet setting forth his plans for the establishment of an electric telegraph; but it was never published. According to his own account he also gave considerable attention to the escapement principle, or step by step movement, afterwards perfected by Wheatstone. While busy in preparing his apparatus for exhibition, part of which was made by a clock-maker in Clerkenwell, he consulted Faraday about the construction of electro-magnets, The philosopher saw his apparatus and expressed his opinion that the 'principle was perfectly correct,' and that the 'instrument appears perfectly adapted to its intended uses.' Nevertheless he was not very sanguine of making it a commercial success. 'The electro-magnetic telegraph shall not ruin me,' he wrote to his mother, 'but will hardly make my fortune.' He was desirous of taking a partner in the work, and went to Liverpool in order to meet some gentleman likely to forward his views, and endeavoured to get his instrument adopted on the incline of the tunnel at Liverpool; but it gave sixty signals, and was deemed too complicated by the directors. Soon after his return to London, by the end of April, he had two simpler instruments in working order. All these preparations had already cost him nearly four hundred pounds.
On February 27, Cooke, being dissatisfied with an experiment on a mile of wire, consulted Faraday and Dr. Roget as to the action of a current on an electro-magnet in circuit with a long wire. Dr. Roget sent him to Wheatstone, where to his dismay he learned that Wheatstone had been employed for months on the construction of a telegraph for practical purposes. The end of their conferences was that a partnership in the undertaking was proposed by Cooke, and ultimately accepted by Wheatstone. The latter had given Cooke fresh hopes of success when he was worn and discouraged. 'In truth,' he wrote in a letter, after his first interview
