The motion of the armature in both of these instruments takes a sensible time, but Alexander Bain, of Thurso, by trade a watchmaker, and by nature a genius, invented a chemical telegraph which was capable of a prodigious activity. The instrument of Bain resembled the Morse in marking the signals on a tape of moving paper, but this was done by electrolysis or electro-chemical decomposition. The paper was soaked in a solution of iodide of potassium in starch and water, and the signal currents were passed through it by a marking stylus or pencil of iron. The electricity decomposed the solution in its passage and left a blue stain on the paper, which corresponded to the dot and dash of the Morse apparatus. The Bain telegraph can record over 1000 words a minute as against 40 to 50 by the Morse or sounder, nevertheless it has fallen into disuse, perhaps because the solution was troublesome. It is stated that a certain blind operator could read the signals by the smell of the chemical action; and we can well believe it. In fact, the telegraph appeals to every sense, for a deaf clerk can feel the movements of a sounder, and the signals of the current can be told without any instrument by the mere taste of the wires inserted in the mouth. A skilful telegraphist can transmit twenty-five words a minute with the single-current key, and nearly twice as many by the double-current key, and if we remember that an average English word requires fifteen separate signals, the number will seem remarkable; but by means of Wheatstone's automatic sender 150 words or more can be sent in a minute.