A. 1. An aeroplane cannot conduct reconnaissance at a height of less than 5,000 feet without being within easy range of anti-aircraft artillery; nor of less than 2,000 feet without coming into range of machine-gun and rifle fire. 2. To be observed from such heights, objects on the ground must be distinguished by: (a) Motion. (b) Color contrast. (c) Line contrast, or (d) Shadows. B. Concealment: 1. (a) On warning of hostile aircraft, troops on the march should withdraw to the side of the road (if possible, into shade), or lie down flat in the road and remain motionless. (b) If it is necessary to continue the march, this should be done in broken detachments, which are far less distinct than continuous column. (c) Troops in a trench should crouch down in the shadowy side and remain motionless. (d) Faces should never be turned up, as the high lights on cheek-bones and foreheads then show up distinctly. (e) Bright metal on arms, equipment and headgear must be kept covered. 2. Artillery wagon-trains, etc., should if possible be halted promptly on warning. When halted, their neutral coloring protects them. 3. Trenches are best concealed: (a) By avoiding, in construction, a too regular outline, and following as far as possible the contours of the ground. (b) By coloring the parapet and parados to match the ground. This may be done most quickly by painted canvas; if the latter is not available, by planting or strewing the loose earth with surrounding herbage. In this work care must be taken not to make the covering itself too conspicuous by brightness or monotony of coloring. (c) By covering the trench itself, where convenient, with a thin material, colored like the parapet and parados. (d) By avoiding all overt movement of troops in the trenches under observation. 4. Buildings, _e.g._, ammunition dumps, hangars, etc., can be completely concealed by being painted the color of the ground they stand on and fitted with canvas curtains, similarly painted and stretched from the eaves to the ground at a horizontal angle of 35 degrees. These curtains completely eliminate shadows. 5. Success in each work of concealment by camouflage is best assured by the assistance of an aeroplane observer to test and correct it. * * * * * Orders Governing Intrenchment Problems at Second Plattsburg Training Camp. HEADQUARTERS PLATTSBURG TRAINING CAMP, PLATTSBURG BARRACKS, NEW YORK. SEPTEMBER 22, 1917. DIVISIONAL ENTRENCHING PROBLEM. General Situation: