TRAIL, SURVEYS. 61 



grade. The surveyor should try his very best to get 

 the trail upon a turnpike grade, but if this is obviously 

 impracticable, he should keep the grade as low as pos- 

 sible, and not exceed 12 per cent. This is the limit 

 for safe mountain roads such as are used for freighting, 

 and might properly be called a freight grade. When 

 trails must be constructed upon grades steeper than 

 this, or to places which roads can not reach for many 

 years, it is simply a case of making the best location 

 the circumstances permit. However, there is still the 

 final limit which should not be exceeded. This is the 

 trail grade of 18 per cent, and is as steep as a loaded 

 pack animal can ascend without violent and exhaustive 

 effort. Long steep grades should have breaks at inter- 

 vals where animals may rest and recover. 



In deciding on a route or location, the following 

 points should be considered. 



(1) A south exposure has less snow, is dryer, often 

 more open, and has an increased fire hazard. 



(2) Slide rock and other unstable material make a 

 temporary or dangerous tread. 



(3) Steep side hills, near the angle of repose, are 

 liable to landslides or snowslides. 



(4) Bridges and temporary structures should be 

 avoided as far as possible. 



(5) The permanence of a trail depends on the material 

 and its drainage. 



It will be seen from the above that the location of a 

 trail grade is almost wholly a matter of experience and 

 good judgment 



