PART III 



FOREST PROTECTION HELIOGRAPHS AND OTHER SIGNALLING 



APPARATUS 



CHAPTER XVIII 



HELIOGRAPH 



Section 98 The Instrument 



The heliograph is a visual signalling device consisting essentially of a plane 

 mirror and certain auxiliary equipment by which flashes of light reflected from the 

 mirror may be directed toward any given point. For purposes of communication these 

 flashes are generally made to form the symbols of the telegraphic code, a short flash 

 representing a dot; a long flash, a dash. 



The heliograph is almost exclusively used as a daylight signalling device only 

 and requires full sunlight for its successful operation. Within certain limits, which 

 will be hereinafter discussed, the heliograph is, next to the telephone, the most useful 

 communication device that is at present available for forest-protection purposes. 



Heliographs are of two main types: (a) Moving flash; (Z>) Fixed flash. 



The first type is represented by the British Army heliograph. The second type 

 is^ represented by the United States Army and the United States Forest Service 

 heliographs. 



Section 99 Use in Forest Protection 



Although the heliograph has been used by the army for the purposes of com- 

 munication for a great many years, its use in forest protection is a recent develop- 

 ment. So far as is known, this instrument was first employed in forest protection for 

 communication between lookout stations under the direction of the author on the 

 Kaniksu National Forest in Idaho in 1909. This successful demonstration of its 

 utility has been followed by a slow but widespread adoption of the instrument for 

 certain restricted uses on a large number of the National Forests of the United States, 

 and at least one instance of its use in Eastern Canada has been noted. The recent 

 invention by Supervisor D. P. Godwin, of the United States Forest Service, of an 

 improved form of heliograph for forest protection purposes, promises to enlarge greatly 

 the sphere of usefulness of this instrument. While realizing fully the limitations of 

 the heliograph, especially for use in the East or in a flat country, the author believes 

 that its capabilities for enabling the members of a specialized forest-protection staff 

 to maintain intercommunication are very far from being fully utilized or even 

 appreciated. 



Heliograph stations as employed in forest protection are of three classes : perman- 

 ent, semi-permanent, and temporary. 



Permanent stations include mountain lookout stations or other fixed points in 

 the forest improvement system where signals may be sent or received with a high 

 degree of dependability during all or part of the fire season. Lookout stations are, 

 from their location and use, heliograph stations of the very first importance, since 

 they not only have a wide range of country constantly under observation but may 

 themselves be picked up with little difficulty from most of the area within their range. 



Semi-permanent stations are those established at or near temporary camps such 

 as fire, survey, or construction camps or near ranger stations that are not connected 

 to the telephone system. Stations of this class will likely be occupied for signalling 



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