The Abney Hand Level. 369 



section lines are supplied with good vertical and horizontal control 

 stakes providing for the double running of the forty. 



3. These sections of land are mapped as carefully as possible 

 by three crews of equal efficiency. 



a. The first crew will make as careful a map as possible using 

 the aneroid. 



b. The second crew will make as careful a map as possible using 

 the Abney. 



c. The third crew will make an absolutely accurate map using 

 the transit. 



Each strip crew will use the same primary control and this con- 

 trol will cost the same for each method. 



4. Careful cost figures will be kept of the work done by each 

 method. 



5. The final maps will be plotted and tracings made of each 

 map. The tracing of the aneroid map will now be laid over the 

 tracing of the transit map and the degree of error absolutely 

 determined. The tracing of the Abney map is then laid over the 

 transit map and the error determined. The cost figures kept will 

 give the total cost of the final map by each method. The ex- 

 perimenter will now have absolute knowledge of the relative ac- 

 curacy and cost of each instrument and method for each type 

 of topography, timber cover, and weather condition. 



The choice of instrument and method can now be made in- 

 telligently in order to obtain the most valuable results, Such a 

 scientific choice of methods by the reconnaissance party chief 

 will result in the obtaining of maps of equal value although the 

 separate portions of the work were done under widely different 

 conditions. The aim always should be to maintain the standard set 

 for the type of map being made. 



In the use of a new instrument and new methods there is in- 

 troduced a loss of time and efficiency which will disappear with 

 practice. This point should be borne in mind when studying the 

 practical value of the method for the use of the Abney Hand Level 

 here proposed. 



