362 forestry Quarterly. 



the streams become rapids, and again the stream will flow upon 

 an underlying shelf of harder rock for some distance on a smooth 

 grade. The compassman can indicate very approximately the 

 changing character of the stream as he encounters it on his strips 

 without an Abney hand level, but when the field man gathers all 

 this data, not haphazardly and by guess alone, but with good 

 judgment aided by a practical instrument, the value of this data 

 is greatly enhanced. 



The logger is interested in the character of the draws, ravines 

 and gullies, and even a rough map should give the logger an ap- 

 proximate idea of his logging chance. 



The draftsman can express the true nature of all the draws and 

 ravines on the final map with the field data furnished by these 

 methods. The inaccessibility or accessibility of timber, from the 

 logger's point of view can be determined approximately from 

 such a map, and the closer examination of the ground can then be 

 made more intelligently. 



The collection of these data may introduce a greater cost on an 

 area basis, but the total cost on a basis of the relative value of 

 the final map will be much lower. 



Office Work in Plotting The Pinal Map. 



With such field data the camp draftsman is called upon to do 

 much of the work usually done by the man in the field. In order 

 to shorten the increased work of the office man as much as pos- 

 sible a profiling scale has been designed as illustrated in Figure 5. 

 This rule is to answer the purpose both of obtaining the eleva- 

 tions of the slope stations on the strip line and of interpolating 

 the contours.* 



The profile in Figure 4 was drawn from the field data on the 

 sample strip shown in the same figure. This profile has been pre- 

 pared in order to illustrate the character of the data and to make 

 the work of the ofiice man more easily understood. 



I. Horizontal Closure. The error of horizontal closure is cor- 

 rected first and this error of closure is distributed along the line 

 between the slope stations pro ratio to the distance between sta- 

 tions. The greater part of the error is thrown between stations 



*See also the following article. 



