LOGGING 



are used to provide a greater bearing surface than that offered 

 by the main sill. 



Mud sills are suited for a bottom solid enough to provide a 

 firm support but they are not adapted for use in swamps or 

 stream beds. The foundations used in the two latter cases 

 consist of piles driven to bed rock, one being placed under the 

 base of each leg, and cut off 2 or 3 feet above high-water mark. 



Pholo&raph by R. C. Hall. 

 Fig. 78. — a Round Timber Framed Trestle on a Lodging Railroad. 

 The large skidway on the right is several feet below the le\el of 

 the track. Alabama. 



Stringers, ties and guard rails are used as on a pile trestle, 

 and the bents are braced in the same manner. 



Cost of Trestles. — Framed trestles are frequently built by 

 contract, the price being regulated by the amount of timber used 

 and the height of the trestle. The labor charge for trestle con- 

 struction where the structure is less than 10 feet in height is from 

 $2 to $4 per thousand feet of timber used, while high trestles may 

 cost from $7 to $10. 



