The Use of the Abney Hand Level. 375 



a sight can be secured on a tree or snag at the further edge of the 

 patch. This should always be done when possible to avoid esti- 

 mating the difference in elevation as the course is projected 

 through the brush. 



Just as big a day's work should ordinarily be accomplished by a 

 two-man crew using the Abney as with the aneroid barometer. 

 We could double run eight forties a day in rather difficult going, 

 and that is certainly satisfactory. 



In our work last winter we ran a transit level through ap- 

 proximately the middle of the area covered by reconnaissance. 

 Absolute bench marks were established at section line intersec- 

 tions and at other points where necessary. From these bench 

 marks, base lines usually 2 miles apart were run with the Abney 

 hand level. In establishing base lines, especially long ones, with 

 the Abney a little more accurate computation is employed than 

 for regular strip cruise work. Distance was measured with a 

 chain and elevations w^ere computed to the nearest foot. Our 

 base line surv^eys w^ith the Abney proved very satisfactory. A 

 two-man crew^ can run and blaze about 2| miles of base line per 

 day. 



T 31 S, R 3 E, within the Crater National Forest, was cov- 

 ered last winter in this kind of a reconnaissance survey, and it 

 is the only large area on the Forest mapped with a high degree 

 of accuracy. 



One valuable feature in using the Abney is the fact that a 

 contour map of any fineness desired can be secured with scarcely 

 any additional work or increased cost. Ten-foot contour inter- 

 vals can be sketched in on the field map as easily as 25 or 5ofoot 

 contours. 



The Abney hand level has undoubtedly come to stay as an 

 instrument useful in reconnaissance work and if the right men 

 are secured to use it, it will supplant the aneroid barometer. 



Some improvements' in the Abney hand level should be made 

 to make it more convenient and less liable to get out of adjust- 

 ment. The graduated arc should have about twice as great a 

 radius. It should be graduated in both degrees and per cent. 

 The tangent graduation should extend to 200 per cent, and the 

 case for it should be arranged so as to carry on the belt instead 

 of over the shoulder. 



