LIFTS

the bane piven Seen eens: dral, | vances for raising vy weights. They fect. | consist easentially of a cage or chamber, hed | which mR ee moving up and down © on | 4 vertical shaft, The cage may be raised by means of oe ee lying | or by means an hydraulic pre as. misjIo the latter case the plonger of that | the pre is placed beneath the floor, the} the pre itself being some distance {the | below the basement. In all cascs, to local | reduce the work, ee cere is counterpoised. the | by a weight about to its own — z: LIGHT, ‘The sensation which is: light is produced when certain rays iraw | proceeding from the sun or other luminous body fa:l upon the retina of the eye. These tadt, | rays are conveyed through the medium mist. | known as cther, which | af be all space ‘aris, | and matter, Light itself tsinvisible, but is | eas or | made visible by the minute dust pariicles later |in the air, The velocity of the light rays His | bas beer determined in various ways, end 3 [s. 197]