CHAPTER II 



METHODS OF CONVEYING INFORMATION TO A DISTANCE 

 Section 14 Variety of Methods Available 



Perhaps the oldest and simplest means by which information may be conveyed 

 from one point to another is by messenger. The most modern and technically com- 

 plex is the wireless telegraph and telephone. Between these two extremes lies the 

 whole knowledge and experience of man in the solution of this problem. This has 

 always been a problem of paramount importance to military forces so that we find 

 in military literature the most complete and exact records of the various methods by 

 which it has been solved. These methods are of the most varied character but may 

 all be divided into two principal classes : the Visual Signals which are received through 

 the sense of sight and the Audible Signals received through the sense of hearing. In 

 order to show the possibilities for selecting methods adapted to particular circum- 

 stances, it is of interest to note briefly the characteristics of the more important types 

 of signals and other means of conveying intelligence to a distance. 



The use of carrier pigeons, so extensively employed in military and nava.l opera- 

 tions, has, so far as the author is aware, never been attempted in forest protection. 

 There seems to be no reason, however, why carrier pigeons could not be very success- 

 fully employed in this work. 



Section 15 Types of Visual Signals 



1 WIGWAG SIGNALS 



This system consists in forming the symbols of the telegraphic code by moving 

 various objects in certain ways with reference to some fixed object. A flag swung to 

 the left or to the right, for instance, the person swinging it acting as the point of 

 reference is a common method of sending wigwag signals. Torches, lanterns, or in 

 fact any object visible at a distance may be similarly employed. Over great distances 

 the beam of an electric searchlight thrown vertically can be used to send messages by 

 wigwag. 



2 SEMAPHORE SIGNALS 



By varying the positions of objects of the same shape with reference to a fixed 

 object, it is possible to form symbols that represent the letters of the alphabet. Thus, 

 the two arms may be so held with reference to the body and to each other as to form 

 all the different symbols needed to send the full alphabet. To extend the range of 

 visibility small flags are held in the hands. Special semaphore machines with movable 

 arms of large size are also used. Within a limited range this system has many 

 advantages, particularly that of speed. 



3 CODE SIGNALS 



Without attempting to send alphabetical symbols it is possible to send pre- 

 arranged messages by the use of objects of different colours or shapes or by a com- 

 bination of both, using one or more of them to represent each code message. Flags 

 of different colours and designs are most commonly employed for this purpose and the 

 system is used for communication by ships at sea and for such purposes as displaying 

 storm warnings or other weather signals. Of course, similar flags of distinctive 

 colour or design may also be used to represent the letters of the alphabet and words 

 spelled out in full. 



4 CHRONOSEMIC SIGNALS 



In all the foregoing systems the time of display of the signal does not form an 

 essential part of the method. Several systems are in use, however, in which time is 



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