38 FOREST REGULATION 



It i's feasible even in high mountain districts to stay below 200 

 acres in the average size of the lot. 



For convenience the lots of one stream valley, or part of one 

 watershed may be combined into a Block, and the lots of each block 

 have their own series of numbers, and the Block is thus made to 

 correspond to the Section in ordinary Survey. See Plate I. The 

 lines of division normally follow the ridges or use the streams and 

 where the distance from stream to top of ridge is too great lines 

 parallel to the valley are established. 



Since roads and trails, normally use ridges and valley, or con- 

 nect these two by oblique lines to suit grade and topography, these 

 roads and trails are used, later on, in perfecting this land division. 

 But even where such a road system is well developed, as in some of 

 the recent European work, the roads rarely make over 40% of all 

 division lines in hill and mountain country, and it is probably a 

 mistake to allow this use in land division to influence unduly the 

 planning of a road system. See plates II and III. 



Of late, efforts have been made to base a detail description and 

 estimate of timber on a partial and more or les's temporary subdi- 

 vision. (See Diagram fig. I.) A set of base lines or "controls'*, 

 tied into a regular United States land survey, are established by use 

 of solar transit and stadia, or chain measurements. From the prin- 

 cipal one of such a series, a number of secondary base lines are run 

 out on the ridges between streams. On all control lines stations 

 are established at regular intervals, and number of station, and 

 altitude marked on monuments, and recorded on map or in book. 

 In this way the area is practically subdivided into tracts of several 

 hundred, to several thousand acres in size. The description and 

 estimate-work then starts at the stations set on the control or base 

 lines, and tries to secure the information, usually by forties. 



If the control lines and their stations are made permanent and 

 maintained in usable condition, this work may be regarded as a 

 partial, permanent land survey and will well justify the expense. 

 If the entire system of lines is temporary and allowed to disappear, 

 the work serves only the purpose of a single survey and is certainly 

 wasteful. In either case the description works on areas and reports 

 on areas not actually marked on the ground, and thus has the short- 



