The Germans had some very unhealthy experiences with the "Q-boats" or "mystery ships" of the British. These were vessels rigged up much like ordinary tramp steamers, but they were loaded with wood, so that they would not sink, and their hatches were arranged to fall open at the touch of a button, exposing powerful guns. They also were equipped with torpedo-tubes, so that they could give the U-boat a dose of its own medicine. These ships would travel along the lanes frequented by submarines, and invite attack. They would limp along as if they had been injured by a storm or a U-boat attack, and looked like easy prey. When a submarine did attack them, they would send out frantic calls for help, and they had so-called "panic" parties which took to the boats. Meantime, a picked crew remained aboard, carefully concealed from view, and the captain kept his eye upon the enemy through a periscope disguised as a small ventilator, waiting for the U-boat to come within range of certain destruction. Sometimes the panic party would lure the submarine into a favorable position by rowing under the stern as if to hide around the other side of the ship. At the proper moment, up would go the white ensign--the British man-of-war flag--the batteries would be unmasked, and a hail of shell would break loose over the Hun. Many a German submarine was accounted for by such traps. [Illustration: (C) Underwood & Underwood A Camouflaged Ship in the Hudson River on Victory Day] Submarines themselves used all sorts of camouflage. They were frequently equipped with sails which they would raise to disguise themselves as peaceful sloops, and in this way they were able to steal up on a victim without discovery. Sometimes they would seize a ship and hide behind it in order to get near their prey. CAMOUFLAGE ON LAND But the call for the wielders of the paintbrush came not only from the sea. Their services were needed fully as much on land, and the making of land camouflage was far more interesting because it was more varied and more successful. Besides, it called for more than mere paint; all sorts of tricks with canvas, grass, and branches were used. Of course, the soldiers were garbed in dust-colored clothing and shiny armor was discarded. The helmets they wore were covered with a material that cast no gleam of light. In every respect, they tried to make themselves of the same shade as their surroundings. Like the Indians, they painted their faces. This was done when they made their raids at night. They painted their faces black so that they would not show the faintest reflection of light. A PAPER HORSE