MANUAL FOR NONCOMMISSIONED OFFICERS. 813 



This relation need not be tisUtj, but may be anything from 

 x^ that an architect might use in mailing a map or plan of a 

 house up to one over a billion and a half, which is about the 

 proportion between map and real distances in a pocket-atlas 

 representation of the whole world on a 6-inch page. Map 

 makers call this relation the " scale " of the map and put it 

 down in a corner in one of three ways. 



For the sake of an illustration, say the relation between 

 map and ground distances is 1 to 100; that is, 1 inch on the 

 map is equal to 100 on the ground. The scale may be written : 



First. 1 inch equals 100. 



Second, y^. 



Third. As shown by figure 3 (p. 259). 



These expressions mean one and the same thing. A varia- 

 tion of the first method on a map of different scale might be : 

 1 inch equals 1 mile. Since a mile contains 63,360 inches, then 

 the real distance between any two points shown on the map is 

 63,360 times the map distance. 



To find the ground distance by the third kind of scale, copy 

 it on the edge of a slip of paper, apply the slip directly to the 

 map, and read off the distance; and so we answer the ques- 

 tion, "How far?" 



After direction and distance comes the interpretation of the 

 signs, symbols, and abbreviations on the map. Those author- 

 ized are given on pages 272 and 273 (a reprint of Appendix 4, 

 Field Service Regulations, 1914) ; but there are a good many 

 other conventional signs in common use. A key to them is 

 published by the War Department and is called " Conven- 

 tional Signs, United States Army." From these you read at 

 once the natural and artificial features of the country shown 

 on your map. It should be borne in mind that these conven- 

 tional signs are not necessarily drawn to scale, as are the 

 distances. They show the position and outline of the fea- 

 tures rather than the size. This for the reason that many of 

 the features shown, if drawn to scale, would be so small that 

 one could not make them out except with a magnifying glass. 

 If the exact dimensions are of any importance, they will be 

 written in figures on the map. For instance, bridges. 



In addition to the above conventional signs, we have con- 

 tours to show the elevations, depressions, slope, and ^ape of 



