60 INSTRUCTIONS FOR MAKING FOREST SURVEYS, ETC. 



The most important thing about a trail is its grade. 

 Any other feature of its construction may be improved 

 from month to month or from year to year, but if the 

 grade is not properly established it must in time be 

 abandoned. Thus, not only may time and money be 

 wasted, but the trail, while in use, would be unsatis- 

 factory. On the other hand, if the grade is properly 

 located, the trail will be useful as soon as it is passable. 



The best gradient between any two points is upon 

 a line which would have the same percentage of rise 

 from beginning to end. Often there are " salient 

 points" along the route, above or below which the 

 grade must run, and we must then think of the line as 

 divided into parts, each with its own percentage of rise 

 between these salient points. If an even gradient is 

 also a low gradient, it is unquestionably the proper 

 location for the trail if construction is practicable. The 

 same is true if the gradient is on the most direct and 

 practical route and is below the maximum for trails. 



Reverse grades should be avoided if possible. This 

 means that we should never go downhill when the 

 object is to go uphill, as this obviously increases the 

 elevation to be climbed, and therefore increases the 

 grade upon the ascending portions of the trail. 



There are three maxima grades for trail construction. 

 These are: 6 per cent, 12 per cent, and 18 cer cent. 

 Being multiples of 6, these are easy to remember, as 

 are also the reasons for having several maxima. A 

 good grade, having a maximum of 6 per cent, may later 

 be developed into a first-class road or turnpike. Such 

 a grade might be called, for convenience, a turnpike 



