252 LOGGING 



(i) Roads in a rolling or rough region should enter the tract 

 at the lowest point and follow natural drainage, because it 

 usually affords the best grade out of the region and the operator 

 can bring his timber to the main line on a down grade. Road- 

 beds along natural drainage should be placed above high -water 

 mark when possible, although on roads which are to be used only 

 for a short period, it may be cheaper to build near the stream and 

 suffer a few washouts rather than incur a very heavy construc- 

 tion expense. 



(2) The shortest possible route is usually desirable, but it is 

 better to increase the length of line if heavy cuts, fills, bridge 

 and trestle construction can be avoided. 



(3) "Velocity" grades are often used to advantage in crossing 

 "draws" or depressions but they are feasible only on straight 

 track, for it is extremely dangerous to run trains at high speed 

 on a curved track which has a descending grade. In addition 

 to their influence on the hauling ability of a locomotive, steep 

 pitches are a disadvantage on a road because the track tends 

 to work towards the lower levels and not only is the expense of 

 maintenance greater than for a fairly level road but also the 

 danger of wrecks is increased. 



(4) Where logging railroads cross ridges or cover sharp 

 changes in grade in a short distance, "switch backs" are usually 

 preferable to doubling back with a curve since the latter method 

 often necessitates a heavier construction expense. Switch backs 

 often are the only means at hand for securing timber from eleva- 

 tions above or below the main line. 



(5) Grades should not exceed 3 per cent and curves should 

 not exceed 12 degrees on roads that are to be used for several 

 years and over which a large amount of timber is to be hauled, 

 although in a rough region these figures are often increased in 

 practice. 



Location in a region without marked topographical relief, such 

 as the flat pineries or the cypress swamps of the South, presents 

 no special difficulties. The main object is to bring the railroad 

 to the timber by the shortest and cheapest route. The con- 

 struction cost is low on dry lands in these regions, because only 



