26 Master Minds of Modern Science 



The light reflected from the scene to be televised is 

 collected by means of a lens — just as it is when focusing 

 a camera — and this light is focused upon the light-sensi- 

 tive cell. Interposed between the cell and the lens are 

 three rapidly revolving discs. The first, bearing a number 

 of round lenses in staggered formation, revolves at a rate 

 of 800 revolutions per minute, and breaks up the image into 

 strips. The second is provided with a large number of 

 radial slots and revolves about 4000 times per minute, 

 further cutting up the light-ray. The third disc has a 

 spiral slot and revolves more slowly. 



The combined effect of these discs is to cause the whole 

 of the image to fall on the light-sensitive cell in a quick 

 continuous chain of tiny areas of varying brilliance in one- 

 tenth of a second. The light reflected from the shadows is 

 naturally dim, while from the high lights of the scene it 

 is comparatively bright. The cell transforms these rapid 

 variations of light into electric-current variations, which 

 are transmitted to the receiving apparatus by wire or 

 wireless after being amplified. 



At the receiver the apparatus is somewhat on the lines 

 of that used at the transmitter, although in a rather 

 simplified form. Similar revolving discs are interposed 

 between the source of light, a glow discharge lamp, and 

 the ground-glass screen. The incoming varying current 

 causes this light to vary in a corresponding manner to the 

 variations of the cell at the transmitter ; the discs break up 

 the light and throw it on the screen reconstructing the 

 scene. Considerable modifications of this earlier appara- 

 tus have been made in the past year or two. 



Since carrying out his first successful television experi- 

 ments Baird has been devoting part of his time to further 

 developments made possible by his own achievements. 

 The most remarkable of these new developments is nocto- 

 vision, or seeing in darkness or fog by means of the 

 electric eye of the televisor. 



