FOREST RAILROADS 255 



out and blazes all section lines; determines distances by pacing, 

 which are checked on quarter-section and section corners; and 

 secures elevations by means of an aneroid barometer. A rough 

 topographic map is prepared from this data and furnishes a basis 

 for the preliminary location. 



Having roughly determined the route of the road, the pre- 

 liminary location follows. The engineer is aided in this work by 

 one or two rod men and two or more axmen, depending on the 

 density of brush along the route. Where an expensive road is to 

 be built, engineers recommend the use of a transit in preliminary 

 work, because of the accuracy demanded in final results. Some 

 use a railroad compass and a hand level of the Abney type both 

 for main lines and spurs. In a fairly level country the railroad 

 compass will meet all needs, in fact some find a small staff com- 

 pass ample. 



The engineer having traveled over the proposed route one or 

 more times and knowing the problems to be solved, locates a line 

 of tangents and sets stakes marked with the station number, at 

 100-foot intervals along the right-of-way. As the line pro- 

 gresses, the engineer, by trial, selects the points which will keep 

 his grades and curves within the limits set for the line. Several 

 trial lines may be necessary to secure a satisfactory grade. 



On spur lines in a rough region and on main lines in a fairly 

 level region, the preliminary survey is dispensed with. A rail- 

 road compass or a box compass is often used in lieu of a transit, 

 and in* many sections the woods' foreman or superintendent 

 replaces the engineer. 



A common method in the pineries of the South is to locate a 

 line of tangents by the use of three 6-foot straight pickets, along 

 which the locator sights, placing center stakes at 100- foot 

 intervals. 



The final location of the line of tangents is followed by the 

 location of curves. Loggers have a number of rule-of-thumb 

 methods of locating curves, which, although inaccurate, are 

 satisfactory for railroads where a high degree of engineering 

 ability is not demanded. Many who use rule-of-thumb methods 

 determine the deflection angle by eye and lay off trial curves, 



