102 



PHOTO-TELEGRAPHY 



along the length of the cylinder, so that the tracer 

 scrapes over them and not along them. In the case 

 of dots the tracer would go in between two adjacent 

 ones very often, or, as its path is at a slight angle 



FIG. 47. Half -tone single line negative image, 

 as ordinarily used for the Telectrograph. 



to the path of a fixed point on the circumference 

 of the cylinder, it would occasionally touch two 

 dots in consecutive lines at once, and interfer- 

 ence would be caused. 



The single -line screen has the effect of breaking 



