METHODS OF MAP MAKING 123 



(see page 188), tying into the marks left. Elevations got 

 by aneroid, corrected by barograph. Numerous modifica- 

 tions of the rectangular system made as required. 



Alternative Methods. 1. On roads the traverse board 

 vvitli chain is undoubtedly the best instrument for making 

 a survey of fair accuracy. The compass and chain might 

 also be used. But when streams are utilized, unless on ice, 

 stadia measurement will be found to be best and quickest. 



2. The level might be dispensed with, and the transit 

 used as a level on the same settings from which it is used 

 to get bearing and distance. This works best on a stream 

 with grade all one way, and, in the case of a party by itself 

 in the backwoods, is probably the best means of getting 

 data of this kind. One additional man is then required 

 for maintenance. 



3. Instead of the strip survey, using compass and chain, 

 compass and pacing may be employed with circular plots 

 for the timber. It may also be better or necessary to 

 discard both rectangular systems, and work out the topog- 

 raphy by means of road lines, passes, etc., controlling 

 features in the lumbering development. 



C. Subdivision and Topographic Survey Combined. 

 The following procedure has been carried out on a con- 

 siderable scale on undivided townships in New England. 

 The methods employed have been found to be cheap and 

 practical, and the maps resulting have stood the tests of 

 use and time. 



1. Boundaries renewed and tract divided into sections 

 by compass and chain. Topographic notes taken; chain- 

 age marks left every quarter mile. Two months' work for 

 a party of seven men. 



2. Elevation of some point above sea level obtained, if 

 possible ; if not, datum plane assumed at or below lowest 

 point on the tract. Level lines run over roads and streams 

 to ponds, camps, and other accessible points, well distrib- 

 uted through the tract. Commonly a week's work for 

 two men. 



3. Detail of topography and timber worked out together. 

 Mountain peaks located by cross bearings; streams and 

 roads by compass and pacing traverse; other features 



