In the New York Sun, of the 19th inst., Dr. J. C. Fay, of Gravesend, L. I., states that a car has been propelled on the Long Island Railroad by a new motive power, which principally consists of springs wound up by a steam engine, and then they give out their power to move the car. He calls it a " perpetual motion" and asserts that more power is given out by the springs than is required to wind them up. No persra acquainted with mechanical philosophy can ever be gulled by such nonsense. No spring can give out quite so much power as that required to wind }t up, because the loss by friction must be subtracted. A boat wa^built about forty five years ago, in this city (New" fork) the paddle wheels of which were to be moved by springs, like the wheels of the railroad car referred to. It was to annihilate steamboats and establish anew era in navigation. When launched, the springs turned the wheels two or three times, then stood stock still, for ever. Such a distinguished fate is in store for the new spring power on the Long Island Railroad.