278 LOGGING 



The DuPont Powder Company recommends, in general, a 

 charge of i^ pounds of 20 per cent dynamite for each foot in 

 diameter of stump, up to 4 feet; above this diameter 2^ pounds 

 per foot in diameter. 



On dry ground one man can bore holes, load, and blow out 

 an average of fifty stumps per day, if they are not widely scat- 

 tered. 



TIMBER WORK 



The construction of trestles, culverts, cribbing, and other 

 timber work is done just previous to track laying. 



Trestles. — These are used in crossing streams and depressions 

 where the cost of a fill would be excessive. They are cheaper 

 to build than heavy fills and when the road is used for a short 

 time only, the trestle timber can be taken up and used on another 

 line. 



They are built in two types known as pile trestles and frame 

 trestles, and are made in sections, called bents, which are spaced 

 12 or 14 feet apart. 



Pile trestles are used largely in stream beds and swampy 

 spots where good foundations for framed trestles cannot be 

 secured. Low pile trestle bents usually consist of three round 

 piles from 12 to 15 inches in diameter, driven in a row across the 

 roadbed. On a standard gauge road one pile is placed in the 

 center of the roadbed and the outer piles are placed from 24 

 to 28 inches on either side of it. On medium height trestles 

 for standard-gauge track four piles are used, the two inner 

 ones being spaced 3 feet apart, center to center, and the outer 

 piles 26 inches, center to center, on either side of the middle 

 ones. 



They are driven with a pile driver to bed rock, or solid bottom, 

 and are sawed off at the required height above ground. A 10 

 by lo-inch, a 12 by 12-inch, or a 15 by 15-inch timber, called 

 a "cap," is drift bolted on top of them with f by 21-inch drift 

 bolts. 



The bents are connected by stringers, each 8 by 14 inches or 

 9 by 16 inches in size, which are placed at right angles on top of 



