PROGRESS IN COLOR PHOTOGRAPH Y—SMILLIE. 237 
a microscope shows a series of fine red and green lines separated by 
narrower blue lines, and to the naked eye examining it by trans- 
mitted light appears gray, due to the mixture of red, green, and blue. 
From a practical point of view, this method, which consists essen- 
tially in leaving between the red and green lines a space which can 
be filled up with the blue, offers several advantages: 
(1) It removes the difficulty of registration after the exposure of 
the screen. 
(2) It avoids all possibility of white interspaces and of overlap- 
ping of two bands of different colors; and 
(3) As blue is the color which appears most intense in the screen, 
it is an advantage that the blue lines should be slightly narrower, and 
thus less visible. 
The screen is coated with a suitable varnish, and is then ready to 
receive the panchromatic emulsion. 
All operations are conducted by a machine which brings the sen- 
sitive plate in contact with the screen negative, and automatically 
adjusts exposure to variations in the temperature and humidity of the 
air. Although the method is used by the originators of the Warner- 
Powrie process for securing screen plates in lines, yet it is equally 
applicable to the making of a screen plate of any form whatever, 
whether of regular geometrical pattern or of irregular grain. 
It will be seen that by the use of these plates a negative in the 
complementary colors may be made by simply developing and fixing. 
This negative is available for making positives on glass to any 
number, or the picture may be developed and the negative image dis- 
solved out, and the remaining bromide of silver exposed to light and 
again developed, and the result will be a positive on glass in the 
correct colors of the original subject. 
