'Whilst completing the model of my original plan,' he wrote to his mother on April 5, 'others on entirely fresh systems suggested themselves, and I have at length succeeded in combining the UTILE of each, but the mechanism requires a more delicate hand than mine to execute, or rather instruments which I do not possess. These I can readily have made for me in London, and by the aid of a lathe I shall he able to adapt the several parts, which I shall have made by different mechanicians for secrecy's sake. Should I succeed, it may be the means of putting some hundreds of pounds in my pocket. As it is a subject on which I was profoundly ignorant, until my attention was casually attracted to it the other day, I do not know what others may have done in the same way; this can best be learned in London.'
The 'fresh systems' referred to was his 'mechanical' telegraph, consisting of two letter dials, working synchronously, 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 with the Professor, 'I had given the telegraph up since Thursday evening, and only sought proofs of my being right to do so ere announcing it to you. This day's enquiries partly revives my hopes, but I am far from sanguine. The scientific men know little or nothing absolute on the subject: Wheatstone is the only man near the mark.'
It would appear that the current, reduced in strength by its passage through a long wire, had failed to excite his electro-magnet, and he was ignorant of the reason. Wheatstone by his knowledge of Ohm's law and the electro-magnet was probably able to enlighten him. It is clear that Cooke had made considerable progress with his inventions before he met Wheatstone; he possessed a needle telegraph like Wheatstone, an alarm, and a chronometric dial telegraph, which at all events are a proof that he himself was an inventor, and that he doubtless bore a part in the production of the Cooke and Wheatstone apparatus. Contrary to a statement of Wheatstone, it appears from a letter of Cooke dated March 4, 1837, that Wheatstone 'handsomely acknowledged the advantage' of Cooke's apparatus had it worked;' his (Wheatstone's) are ingenious, but not practicable.' But these conflicting accounts are reconciled by the fact that Cooke's electro-magnetic telegraph would not work, and Wheatstone told him so, because he knew the magnet was not strong enough when the current had to traverse a long circuit.
Wheatstone subsequently investigated the conditions necessary to obtain electro-magnetic effects at a long distance. Had he studied the paper of Professor Henry in SILLIMAN'S JOURNAL for January 1831, he would have learned that in a long circuit the electro-magnet had to be wound with a long and fine wire in order to be effective.
As the Cooke and Wheatstone apparatus became perfected, Cooke was busy with schemes for its introduction. Their joint patent is dated June 12, 1837, and before the end of the month Cooke was introduced to Mr. Robert Stephenson, and by his address and energy got leave to try the invention from Euston to Camden Town along the line of the London and Birmingham Railway. Cooke suspended some thirteen miles of copper, in a shed at the Euston terminus, and exhibited his needle and his chronometric telegraph in action to the directors one morning. But the official trial took place as we have already described in the life of Wheatstone.
The telegraph was soon adopted on the Great Western Railway, and also on the Blackwall Railway in 1841. Three years later it was tried on a Government line from London to Portsmouth. In 1845, the Electric Telegraph Company, the pioneer association of its kind, was started, and Mr. Cooke became a director. Wheatstone and he obtained a considerable sum for the use of their apparatus. In 1866, Her Majesty conferred the honour of knighthood on the co-inventors; and in 1871, Cooke was granted a Civil List pension of L100 a year. His latter years were spent in seclusion, and he died at Farnham on June 25th, 1879. Outside of telegraphic circles his name had become well-nigh forgotten.