Rensselaer Union and Jasper Republican, Volume 8, Number 38, Rensselaer, Jasper County, 8 June 1876 — A Machine that Movies by Light. [ARTICLE]

A Machine that Movies by Light.

From the multitudes that crowd the sidewalk of the west side of Union Square, New York city, many are attnteted by a small machine tliar ts in con stant motion, but without any visible mofive power. In front of the instrument, which is in a front window, is a placard averring that perpetual motion is attained by the radiometer, the invention of Prof. William Crookes, F. R. S., of London. The claim is an exaggeration, as the radiometer movei only when struck by ravs of light, and is therefore no more perpetual motion than is a windmill. The in strument moves by the attractive and repulsive powerof light, and by means of a delicate scale can, it is said, be made to weigh light to the one-millionth part of a grain. The radiometer consists of four pith discs, black on one side and white on the other, fastened thp end of four

arms that are connected with a metal or Jewel point in the center. This point spins in a glass oup at the top of a rod which is fastened in an upright position in what the maker says is *a perfect vacuum. -'This vacuum is the Interior of a grass vessel qhaped like an inverted or very fat thennometrical tube, the four discs revolving in the bulb at the top. The light striking on the white surfaces of the discs attracts them, and striking on the black sides repels them, so that the four discs revolve like the sails of a windmill. In the strong sunlight they move with such rapidity as to be undistinguishable; in reflected light their motion is much slower.