December. 1911. 



KNOWLEDGE. 



461 



Figure 3. 

 One h.ilf of tho !;creen. 



Fir.i'RE 4. The dots enlartred from a .screen negative. 



FiGLKL. 5. 



If this pictnrc is held at a distance from the eye the eftect of the The cross lines of the screen, 

 photosjraph will be seen. It is part of Fit;ure 10. 



a ruled screen (see Figure 2), which is made by gets cut uj) into a series of dots and squares 



having two diagonall\-ruled glass plates sealed — ranging gradualK- from fine black dots in the 



together — the result being a cross-lined mesh transparent parts of the negative to squares in 



(see Figure 5). The image passing through this the half-tones and transparent dots in the high 



FiGi l^l I'. Printing. 



FlGL'RE /. Firing the Pl.ite. 



