The plan of construction devised by Professor Morse for the experimental line of telegraph to be erected between Washington and Baltimore, under the Congressional appropriation, provided for placing insulated wires in a lead pipe underground.  This was to be accomplished by the use of a specially devised plough of peculiar construction, to be drawn by a powerful team, by which means the pipe containing the electric conductors was to be automatically deposited in the earth.  This apparatus was entirely successful in operation, and the pipe was thus buried to the complete satisfaction of all concerned, at a cost very much lower than the work could have been accomplished in any other manner.  Two wires were to be used to form a complete metallic circuit, for at that time it was not known, as was shortly afterward discovered, that the earth could be used to form one-half of the circuit.  For purposes of insulation the wires were neatly covered with cotton-yarn and then saturated in a bath of hot gum-shellac, but this treatment proved defective in insulating properties, for when ten miles of line had been completed the wires were found to be wholly useless for electric conduction.

No mode had been devised for the treatment of india-rubber to make it available for purposes of insulation, and gutta-percha was wholly unknown as an article of use or commerce in this country.  Twenty-three thousand dollars of the Government appropriation had been expended, and the work thus far accomplished was an acknowledged failure.  Only seven thousand dollars of the available fund remained unexpended, and this was regarded as inadequate to complete the undertaking under any other plan.  The friends of the enterprise were in despair, and for some time saw no other alternative than to apply to Congress for an additional appropriation.  This, however, was regarded as almost hopeless, and the difficulty of the situation was extremely embarrassing.

An amusing incident was related of the means used to keep from public knowledge the desperate situation.  Professor Morse finally visited the scene of activity where the pipe-laying was proceeding, and, calling the superintendent aside, confided to him the fact that the work must be stopped without the newspapers finding out the true reason of its suspension.  The quick-witted superintendent was equal to the occasion, and, starting the ponderous machine, soon managed to run foul of a protruding rock and break the plough.  The newspapers published sensational accounts of the accident and announced that it would require several weeks to repair damages.  Thus the real trouble was kept from the public until new plans could be determined upon.

After long and careful consideration, Professor Morse very reluctantly decided to erect the wires on poles.  This plan was, at first, considered wholly objectionable, under the apprehension that the structure would be disturbed by evil-minded persons.  It had, however, become manifest that this was the only mode of construction that could be accomplished within the remainder of the appropriation, and, finally, upon ascertaining that pole lines had already been adopted in England, it was determined to proceed in this manner.  The line was thus completed between Washington and Baltimore about May 1, 1844, and proved to be successful and in every way satisfactory in its operation.