The receiving-instrument consisted of a type-wheel and means for driving it. It was somewhat complicated, and can only be described in a general way. If the cylinder of the transmitter was set to rotating it would break and close twenty-eight times each revolution. (There were fourteen closes and fourteen breaks, each break and each close of the current representing a step.) The type-wheel of the receiver was divided into twenty-eight parts, having twenty-six letters and a dot and space, each break moved it one step and each close a step; so that if the cylinder, with its twenty-eight pins, started in unison with the type-wheel, with its twenty-eight letters and spaces, they would revolve in unison. The keys were lettered, and if any one was depressed the pin corresponding to it on the cylinder would strike it and stop the rotation of the cylinder, which stopped the breaking and closing of the circuit, which in turn stopped the rotation of the type-wheel--and not only stopped it, but also put it in a position so that the letter on the type-wheel corresponding to the letter on the key that was depressed was opposite the printing mechanism. The printing was done on a strip of paper, which was carried forward one space each time it printed. The printing mechanism was so arranged that so long as the wheel continued to rotate it was held from printing, but the moment the type-wheel stopped it printed automatically. The messages were delivered on strips of paper as they came from the machine. In 1855 David E. Hughes of Kentucky patented a type-printing telegraph that employed a different principle for rotating the type-wheel. The electric current was used for printing the letters and unifying the type-wheels with the transmitting-apparatus. The transmitter, cylinder, and the type-wheel revolved synchronously, or as nearly so as possible, and the printing was done without stopping the type-wheel. Whenever a letter was printed the type-wheel was corrected if there was any lack of unison. This type of machine in a greatly improved form is still used on some of the Western Union lines, especially between New York, Boston, Philadelphia, and Washington. It is also in use in one of its forms in most of the European countries. CHAPTER XIII. MULTIPLE TRANSMISSION.