In the year 1833 a model flying-machine was constructed by Rufus Porter, of New Britain, Conn., who kept experimenting, until about fourteen years later he produced a model propelled by steam, which he exhibited at Washington and at the Merchants' Exchange, New York, and a journal of the day declared "it made the circuit of the rotunda eleven times like a thing animated with life." Still later he constructed a full working machine, but which he never completed because it was found impossible to procure a varnish or coating for the canvas covering which would prevent the leakage of the gases to an extent that wholly destroyed the lifting power of the balloon. The balloon was cigar-shaped, and a little below was suspended a car, conforming on a small scale to the shape of the balloon, which carried the motive power for propelling the whole, and was provided with a pair of screw propellers and a four-leaved rudder. In 1869 Mr. Porter's principle was revived, with certain additions, at Shell Mound Lake, Cal., by Frederick Marriot, and operated by a small steam-engine. The apparatus worked well in a still atmosphere, but proved a failure in brisk winds.