Ma)tchestcy Memoirs, \'ol. Ixiii. (1919) No. 4 



Plate II. 



Illustrates the effect of superposing screens with black lines on white ground. 



Pitch of screens 100 to the inch ; angle 2^°. (Actually, the screens are 



almost of the "chess hoard " type, but the general effect is clear). 



* « %, *\ 



//.. o. 

 Same as in J'ig. 5, but angle is now 5 



