In 1824 the wave of enthusiastic sympathy for the Greeks which swept over the country upon receipt of the tidings of their revolt against Turkish tyranny stimulated Mr. Cooper to invent a torpedo boat, to be steered from the shore by "two steel wires, like the reins of a horse." But on the trial trip of the boat a ship crossed and broke the wires when about six of their total length of ten miles had been let out. The delay made the invention too late for use by the Greeks, and it was not further pursued. About 1835 the subject of aerial navigation had in the United States one of its periodical revivals. Mr. Cooper, believing that a motive power developed from materials of small weight was essential to the solution of the problem, resolved to employ the explosive force of chloride of nitrogen,--one of the most dangerous compounds known to chemists. The result of his experiments in this direction was an explosion which blew his apparatus to pieces, and nearly cost the audacious inventor an eye. In fact, though the organ was saved from total destruction, it was permanently injured. The conveyance of freight by aerial cables--a method now widely used--was practiced by Mr. Cooper at an early day. The use of elevators in buildings was foreseen and provided for by him in the erection of the Cooper Union building, and in that building also he introduced for the first time iron beams as part of a fire-proof construction. In these and other inventions his prophetic intuitions were illustrated. But such intuitions do not fully take the place of scientific training; and one of the inventions of Peter Cooper--which he considered for many years, and possibly to the very last, as his crowning achievement--was a curious example of misdirected ingenuity. It is worthy of notice here, however, for another reason, namely, because of its accidental association with one of its inventor's most remarkable triumphs. As a young apprentice he had studied the steam engine, and had resolved that he would improve it by doing away with the crank. To his mind this was a source of great loss of power, and he believed that, if he could transform the rectilinear motion of the piston rod directly into rotary motion without the intervention of the crank, he would effect a notable economy.