le idea.

A mural painter of New York, William Andrew Mackay, who had long
experimented in the chemistry of color (he is now a member of the staff
of navy camoufleurs), had applied a process of low visibility to naval
vessels long before war broke out in Europe. The basis of his theory of
camouflage was that red, green, and violet, in terms of light, make
gray; they don't in pigment.

The Mackay scheme of invisibility will be easily grasped by the reader
if we take the example of the rainbow. The phenomenon of the rainbow,
then, teaches us that what we know to be white light, or daylight, is
composed of rays of various colors. If an object, say the hull of a
vessel at sea, prevents these rays from coming to the eye, that hull, or
other object, is of course clearly defined, the reason being that the
iron mass shuts out the light-rays behind it. Mr. Mackay discovered that
by applying to the sides of a ship paint representing the three
light-rays shut out by the vessel's hull--red, green, and violet--the
hull is less visible than a similar body painted In solid color.

In a series of experiments made under the supervision of the Navy
Department after we entered the war an oil-tanker ship was so
successfully painted in imitation of the color-rays of light that, at
three miles, the tanker seemed to melt into the horizon. The effect was
noted in the morning, at noon, and in the evening. In the case of
various big liners, more than 500 feet long, no accurate range could be
made for shelling at from three to five miles--the usual shelling
distance--while at eight miles the vessels melted into the ocean-mists.

But the first trials of the system were conducted at Newport, in 1913,
in conjunction with Lieutenant Kenneth Whiting, of the submarine
flotilla. After a period experiments were continued at the Brooklyn Navy
Yard. In 1915 Commander J. O. Fisher, U.S.N., painted the periscope of
his submarine--the K-6--with the colors of the spectrum. Mr. Mackay got
in touch with this officer and explained the work he had done with
Lieutenant Whiting. Fisher, deeply interested, invited the painter to
deliver a series of lectures to the officers of the submarine flotilla
at the Brooklyn Navy Yard.

With the aid of a Maxwell disk--a wheel upon which colored cardboard is
placed and then revolved--he demonstrated the difference between paint
and light, as set forth in a book on the chemistry of color by the late
Ogden N. Rood, of Columbi