CHAPTER XI WARRIORS OF THE PAINT-BRUSH When the great European war broke out, it was very evident that the Entente Allies would have to exercise every resource to beat the foe which had been preparing for years to conquer the world. But who ever imagined that geologists would be called in to choose the best places for boring mines under the enemy: that meteorologists would be summoned to forecast the weather and determine the best time to launch an offensive; that psycologists would be employed to pick out the men with the best nerves to man the machine-guns and pilot the battle-planes? Certainly no one guessed that artists and the makers of stage scenery would play an important part in the conflict. But the airplane filled the sky with eyes that at first made it impossible for an army to conceal its plans from the enemy. And then there were eyes that swam in the sea--cruel eyes that belonged to deadly submarine monsters, eyes that could see without being seen, eyes that could pop up out of the water at unexpected moments, eyes that directed deadly missiles at inoffensive merchantmen. They were cowardly eyes, too, which gave the ship no opportunity to strike back at the unseen enemy. A vessel's only safety lay in the chance that out in the broad reaches of the ocean it might pass beyond the range of those lurking eyes. It was a game of hide-and-seek in which the pursuer and not the pursued was hidden. Something had to be done to conceal the pursued as well, but in the open sea there was nothing to hide behind. HIDING IN PLAIN SIGHT There is such a thing as hiding in plain sight. You can look right at a tree-toad without seeing him, because his colors blend perfectly with the tree to which he is clinging. You can watch a green leaf curl up and shrivel without realizing that the curled edge is really a caterpillar, cunningly veined and colored to look just like a dying leaf; and out in the woods a speckled bird or striped animal will escape observation just because it matches the spotted light that comes through the underbrush. Nature is constantly protecting its helpless animals with colored coats that blend with the surroundings. Long ago clumsy attempts at concealment were made when war-vessels were given a coat of dark-gray paint which was supposed to make them invisible at a distance. Actually the paint made them more conspicuous; but, then, concealment did not count for very much before the present war. It was the eyes of the submarines that brought a hurry call for the artists, and up to them was put the problem of hiding ships in plain sight. A new name was coined for these warriors of the paint-brush: _camoufleurs_ they were called, and their work was known as _camouflage_. MATCHING THE SKY Of course, no paint will make a ship absolutely invisible at a short distance, but a large vessel may be made to disappear completely from view at a distance of six or seven miles if it is properly painted.