With reference to period of visibility, signals are of two kinds, transient and permanent. A transient signal is one which disappears as soon as completed; a permanent signal is one that remains in view for some time. Heliograph signals are transient signals, while signals made by code flags are permanent signals. Signals are divided into classes in accordance with the number of elements employed in their formation. Thus, signals using two elements are signals of the second class, signals using three elements signals of the third class, etc. The standard apparatus used in visual signaling is fully described in a succeeding chapter. Some of the instruments employed are used wholly for day, and some wholly for night, signaling. Some devices, either with or without slight variations, are equally well adapted to day or night work. Visual signaling presents a great field for ingenious and resourceful work, and emergency will often demand the advantageous employment of other methods than those described herein. CHAPTER II. VISUAL SIGNALING EQUIPMENT. THE WAND. The wand is a stick of light wood about 18 inches long and one-half inch in diameter. It is held loosely between the thumb and forefinger and waved rapidly to the right or left to indicate the elements of the alphabet. It is used for practice purposes and the signals made by it are only intended to be read at very short distances. THE FLAG KIT. Two kinds of flag kits, the 2-foot kit and the 4-foot kit, are issued by the Signal Corps. _The 2-foot kit._--This kit consists of one white and one red signal flag, two three-jointed staffs, and a suitable carrying case to contain the outfit. The white flag is made of white muslin 2 feet square, with an 8-inch turkey-red muslin center. The red flag is of similar size and material, the only difference being an alternation of colors in the body and center. The means of attachment to the staff consists of a loop at the center, and two ends of white tape at each edge, of the back of the flag body. The staff is made of hickory in three joints, each 23 inches long, and is assembled by telescoping into brass ferrules. Brass eyes are provided on the first and second joints to receive the tape ends at the edge of the flag. The carrying case, of convenient size and shape to contain the two flags and staffs complete, is made of 8-ounce standard khaki bound with leather and fitted with a shoulder strap. The 2-foot kit is essentially a practice kit, although under favorable conditions of weather and terrain it may be used to advantage as a short distance service signaling outfit. Two of these kits are issued to each troop, battery, and company for the purpose of disseminating general instruction in military signaling throughout the army.