314 MANUAL FOR NONCOMMISSIONED OFFICERS. 



the ground. Abroad, hachures are much used, but they serve 

 only to indicate elevation, and, as compared to contours, are 

 of little value. Contours resemble the lines shown in figure 4 

 (p. 259). 



Hachures are shown in figure 5 (p. 259), and may be found 

 on any European map. They simply show slopes, and, when 

 carefully drawn, show steeper slopes by heavier shading and 

 gentler slopes by the fainter hachures. The crest of the moun- 

 tain is within the hachures. (See fig. 5, p. 259.) 



Contours. — ^A certain student, when asked by his instructor 

 to define " space," said : " I have it, sir, in my head, but can 

 not put it into words." The instructor replied : " I suppose 



that under those circumstances, Mr. , the definition 



really would not help much." And so it is with contours — the 

 definition does not help much if you know a contour when you 

 meet it on a map. For examples of contours, turn to .the map 

 facing page 274, and, starting at the United States peniten- 

 tiary, note the smooth, flowing, irregular curved lines marked 

 880, 860, .840, 840, 860, etc. 



The only other lines on the map that at all resemble con- 

 tours are stream lines, like " Corral Creek," but the stream 

 lines are readily distinguished from contours by the fact that 

 they cross the contours squarely, while the contours run 

 approximately parallel to each other. Note the stream line 

 just to the west of South Merritt Hill. 



The contours represent lines on the ground that are horizon- 

 tal and whose meanderings follow the surface, just as the edge 

 of a flood would follow the irregularities of the hills about it. 

 Those lines that contours stand for are just as level as the 

 water's edge of a lake, but horizontally they w^ander back and 

 forth to just as great a degree. 



The line marked 880, at the penitentiary, passes through on 

 that particular piece of ground every point that is 880 feet 

 above sea level. Should the Missouri River rise in flood to 

 880 feet, ^lie penitentiary would be on an island, the edge of 

 which is marked by the 880 contour. 



Contours show several ichings ; among them the height of the 

 ground they cross. Usually the contour has labeled on it in 

 figures the height above some starting point, called the datum 

 plane — generally sea level. If, with a surveying instrument, 



