The electro-magnet which actuated the receiving instrument in the crude set in use by Morse in 1835 had but a few turns of thick wire.  Professor Henry, by his experiments five years earlier, had demonstrated that many turns of small wire made the electro-magnet far more sensitive.  Morse made this improvement in his own apparatus.  In 1832 Henry had devised a telegraph very similar to that of Morse by which he signaled through a mile of wire.  His receiving apparatus was an electro-magnet, the armature of which struck a bell.  Thus the messages were read by sound, instead of being recorded on a moving strip of paper as by Morse’s system.  While Henry was possibly the ablest of American electricians at that time, he devoted himself entirely to science and made no effort to put his devices to practical use.  Neither did he endeavor to profit by his inventions, for he secured no patents upon them.

Professor Henry realized, in common with Morse and others, that if the current were to be conducted over long wires for considerable distances it would become so weak that it would not operate a receiver.  Henry avoided this difficulty by the invention of what is known as the relay.  At a distance where the current has become weak because of the resistance of the wire and losses due to faulty insulation, it will still operate a delicate electro-magnet with a very light armature so arranged as to open and close a local circuit provided with suitable batteries.  Thus the recording instrument may be placed on the local circuit and as the local circuit an opened and closed in unison with the main circuit, the receiver can be operated.  It was the relay which made it possible to extend telegraph lines to a considerable distance.  It is not altogether clear whether Morse adopted Henry’s relay or devised it for himself.  It is believed, however, that Professor Henry explained the relay to Professor Gale, who in turn placed it before his partner, Morse.

By 1837 Morse had completed a model, had improved his apparatus, had secured stronger batteries and longer wires, and mastered the use of the relay.  It was in this year that the House of Representatives ordered the Secretary of the Treasury to investigate the feasibility of establishing a system of telegraphs.  This action urged Morse to complete his apparatus and place it before the Government.  He was still handicapped by lack of money, lack of scientific knowledge, and the difficulty of securing necessary materials and devices.  To-day the experimenter may buy wire, springs, insulators, batteries, and almost anything that might be useful.  Morse, with scanty funds and limited time, had to search for his materials and puzzle out the way to make each part for himself with such crude tools as he had available.  Need we wonder that his progress was slow?  Instead we should wonder that, despite all discouragements and handicaps, he clung to his great idea and labored on.