368 Forestry Quarterly. 



real index of its value and the cost of a map on an area basis alone 

 is not a fair measure of the efficiency of the methods used in the 

 preparation of the map. 



Experimental mapping with the Aneroid Barometer and 

 the Abney Level. 



Under certain conditions the use of the aneroid is accompanied 

 with so many objections that the choice of another instrument 

 would be decided upon provided the new method was of proven 

 value. However, if such methods deserve any attention at all 

 they ought to be given a thorough trial experimentally first. 



The experimenter has in mind the following sets of conditions : 



1. There are two broad types of topography. The first type 

 is the uniformly sloping type where the slopes are not very steep. 

 The second type is the broken and rugged type. 



2. Further there are two kinds of timber cover. Where the 

 trees are mostly of one species the estimator will work fast. 

 Where there are many species the estimator will work slowly. 



3. There are two kinds of weather conditions, the settled, and 

 the unsettled. 



All of these three factors will enter into the experiment. Each 

 of these factors influences the accuracy of the work done with the 

 aneroid or else have such an influence that the compass man may 

 have spare time to use slower but more accurate methods than 

 the method with the aneroid. 



The degree of accuracy to be attained in the work is fixed and 

 uniform. The object of the experiment shall be to determine with 

 what instrument and with what method can we secure this de- 

 gree of accuracy at the lowest cost, under the conditions existing 

 at the time the work is being done. 



In this problem it is understood that the aneroid is incapable 

 of recording changes in elevation of less than 25 feet accurately. 

 Country so flat as to fall within that class is not considered in 

 this connection. 



Experiments could be made as follows : — 



1. A section, 640 acres, is selected to represent a type. 



2. Base lines are established for this section of land to be used 

 for this experiment. Let us assume that the north and south 



