482 Transactions of the Society. 



just disappeared at a distance from the eye equal to 17 in. 

 (inch = 2 • 54 cm.), the gauze containing 46 meshes to the inch. 

 On the other hand, a single wire * 034 in. in diameter remained 

 fairly visible up to a distance of 20 ft. or 240 in. The ratio 

 between the angles subtended by the periodic structure of the 

 gauze and the diameter of the wire was thus 



•022 x 240 9>L 



•034 17 



Using this in (98), we find for the proportional loss of illumina- 

 tion at the centre of the wire 



i=A--ii, 



T ' 



about what might have been expected. 



Teeling Place, Witham. 



