On December 12, 1846, Bain, who was staying in Edinburgh at that time, patented his greatest invention, the chemical telegraph, which bears his name. He recognised that the Morse and other telegraph instruments in use were comparatively slow in speed, owing to the mechanical inertia of the parts; and he saw that if the signal currents were made to pass through a band of travelling paper soaked in a solution which would decompose under their action, and leave a legible mark, a very high speed could be obtained. The chemical he employed to saturate the paper was a solution of nitrate of ammonia and prussiate of potash, which left a blue stain on being decomposed by the current from an iron contact or stylus. The signals were the short and long, or 'dots' and 'dashes' of the Morse code. The speed of marking was so great that hand signalling could not keep up with it, and Bain devised a plan of automatic signalling by means of a running band of paper on which the signals of the message were represented by holes punched through it. Obviously if this tape were passed between the contact of a signalling key the current would merely flow when the perforations allowed the contacts of the key to touch. This principle was afterwards applied by Wheatstone in the construction of his automatic sender. The chemical telegraph was tried between Paris and Lille before a committee of the Institute and the Legislative Assembly. The speed of signalling attained was 282 words in fifty-two seconds, a marvellous advance on the Morse electro-magnetic instrument, which only gave about forty words a minute. In the hands of Edison the neglected method of Bain was seen by Sir William Thomson in the Centennial Exhibition, Philadelphia, recording at the rate of 1057 words in fifty-seven seconds. In England the telegraph of Bain was used on the lines of the old Electric Telegraph Company to a limited extent, and in America about the year 1850 it was taken up by the energetic Mr. Henry O'Reilly, and widely introduced. But it incurred the hostility of Morse, who obtained an injunction against it on the slender ground that the running paper and alphabet used were covered by his patent. By 1859, as Mr. Shaffner tells us, there was only one line in America on which the Bain system was in use, namely, that from Boston to Montreal. Since those days of rivalry the apparatus has never become general, and it is not easy to understand why, considering its very high speed, the chemical telegraph has not become a greater favourite. In 1847 Bain devised an automatic method of playing on wind instruments by moving a band of perforated paper which controlled the supply of air to the pipes; and likewise proposed to play a number of keyed instruments at a distance by means of the electric current. Both of these plans are still in operation.