electro-magnetic and chemical recording telegraph, substantially and essentially as it now exists," and had invented an alphabet of signs, the same in all important respects as that now in use. "The testimony to the paternity of the idea in Morse's mind, and to his acts and drawings on board the ship, is ample. His own testimony is corroborated by all the passengers (with a single exception), who testified with him before the courts, and was considered conclusive by the judges; and the date of 1832 is therefore fixed by this evidence as the date of Morse's conception, and realization also--so far as the drawings could embody the conception--of the telegraph system which now bears his name." But though invented in 1832, it was not until 1835 (during which time he was engaged in the discharge of the duties of his professorship in the University of the City of New York) that he was enabled to complete his first recording instrument. This was but a poor, rude instrument, at the best, and was very far from being equal to his perfected invention. It embodied his idea, however, and was a good basis for subsequent improvements. By its aid he was able to send signals from a given point to the end of a wire half a mile in length, but as yet there was no means of receiving them back again from the other extremity. He continued to experiment on his invention, and made several improvements in it. It was plain from the first that he needed a duplicate of his instrument at the other end of his wire, but he was unable for a long time to have one made. At length he acquired the necessary funds, and in July, 1837, had a duplicate instrument constructed, and thus perfected his plan. His telegraph now worked to his entire satisfaction, and he could easily send his signals to the remote end of his line and receive replies in return, and answer signals sent from that terminus. Having brought it to a successful completion, he exhibited it to large audiences at the University of New York, in September, 1837. In October, 1837, Professor Morse filed a caveat to secure his invention, but his patent was not obtained until 1840.