_The 4-foot kit._--This kit is of essentially the same description as the 2-foot kit except as regards size. The flags are 3 feet 9 inches square with 12-inch centers and the staffs are considerably heavier, the joints being each 36 inches long. The 4-foot kit is the standard field flag kit and the range at which signals can be exchanged with it depends on a variety of factors, such as the condition of the weather, the location of stations, the proficiency of signalmen, etc. The speed for continuous signaling is seldom greater than five to six words per minute. _Care of flag material._--Signal flags should be examined at the close of drill or practice and repairs made to any rents or loose ties discovered. Flags, when soiled, should be thoroughly washed and dried in the sun. Signals made by clean flags are much more easily read than those made by dirty ones. Staffs should be handled with care, especially when jointing or unjointing. Care should be taken not to bruise the ends of the brass ferrules. If a ferrule becomes loose on a staff it should be tightened without delay. _Powers and limitations of flag signaling._--The advantages which may be claimed for this method of signaling are portability of apparatus, adaptability to varied weather conditions, and great rapidity of station establishment. The disadvantages are the lack of celerity of the signals, their impenetrability to dust or smoke, and the comparatively short ranges at which they can be read. THE HELIOGRAPH. The heliograph is an instrument designed for the purpose of transmitting signals by means of the sun's rays. _Historical._--Experiments with the heliograph with a view to its adoption as a part of the visual signaling equipment of the United States Army were commenced as early as 1878. The reported successful use of the instrument by the British in India about this time led to the importation of two heliographs of the Mance pattern. A series of experiments with these machines conducted for the purpose of eliminating certain objectionable features finally resulted in the evolution of the present type of service heliograph. The early English heliograph was not provided with a shutter, the flash being directed on the distant station by means of a movable mirror controlled by a key. The great objection to this type of instrument was the impossibility of maintaining accurate adjustment during the transmission of signals due to the fact that the manipulation of the mirror tended to throw the flash constantly out of alignment. To overcome this, the American heliograph has been provided with a screen designed to operate as a shutter and control the flash reflected from an immobile mirror. _Description._--The service heliograph equipment of the Signal Corps consists of: A sole-leather pouch with shoulder strap containing-- 1 sun mirror. } 1 station mirror. } Inclosed in a wooden box. 1 screen, 1 sighting rod, 1 screw-driver.