The other colour processes now used with success also are based upon the colour screen.
The process known as the omnicolore, which was brought out in France, depends upon a screen consisting of a very fine network of violet lines in one direction, crossed by red and green lines at right angles. The usual sensitive emulsion is placed over these. The lines run more than two hundred to the inch but they can be seen by close examination of the plate.
In the Thames process which was brought out in England the colour screen and the sensitive emulsion are on separate plates which must be bound together during exposure and again placed in register or in exactly the same relative position after development. This causes some trouble, but reduces expense as the failures waste the sensitive plates but not the colour screens. The primary colours instead of being scattered at random, as in the autochrome system, are arranged in a pattern to give the proper proportions to each. The red-orange and green particles are arranged in circles, with the green a little larger than the red ones, while the blue particles fill the spaces.
THE NEWEST ELECTRIC LIGHTS
One evening our boy friend entered the scientist's laboratory and found it more brilliantly illuminated than it ever had been before.
"Oh, I know," he said looking up at the ceiling, "those new electric lights up there are tungsten lamps. It certainly makes a difference in the looks of this place."
"Lights up all the dingy corners, doesn't it?" answered his friend. "You remember," he continued, "we talked last week about some of the new kinds of electric light and that made me think that I might just as well take advantage of what other scientists have done and install this newest kind of electric lamps."
From the ceiling were suspended several stationary fixtures with bright glass reflectors. The lamps the boy saw were somewhat larger than the usual electric light bulbs, and gave off a beautiful white light instead of the slightly yellowish illumination that comes from the ordinary ones. He saw that the filament from which the illumination came was not arranged in a series of horseshoe curves, as in the case of the ordinary globes, but that it was strung between the ends of cross trees, or "spiders," so that there was a greater total length of filament in the same size bulb than in the ones used before the invention of the tungsten lamp. It is a sight familiar enough to most boys in these days of the rapid adoption of new inventions, but it brought to the boy's mind a question that had often occurred to him before.
"Who invented tungsten lights?" he asked.
"Well, it would hardly be right to say that any one individual invented them, for they were really a development of science worked out by many men, who studied the problem for many years. This caused a number of very bitter lawsuits over the patents and brought about the imprisonment of one United States patent office official who was convicted of falsifying the records at Washington to help one of the inventors. This inventor was John Allen Heany, and his patents were rejected finally, the rights of the tungsten filament going to the General Electric Company. The name 'tungsten' is taken from the material of which filament, or the little wire which lights up in the globe, is made."