The Ahney Hand Level. 367 



the graduation representing O feet is placed upon the station 

 5480. This station is on the contour. Reading to the 20 foot 

 graduation the first contour 5460 is found to be about 6 chains 

 from station 5480. 



2. On the strip ending with station 5470, the last slope read- 

 ing is 8%. The elevation of the last station is 5470, ten feet above 

 the 5460 contour. Taking the rule graduations for the 8% slope 

 the 10 foot graduation is placed upon the station 5470. Reading 

 to the 20 foot graduation the next 20 foot contour 5460 is found 

 to be about two chains from the slope station 5470. 



Observe that this system is identical v/ith Chapman's method ; 

 the only difference being that this adaptation is a mechanical solu- 

 tion of every problem, and that the office man can perform the 

 work with speed. 



A thorough study of figure 4 will explain the character of 

 this rule. The graduations represent the drop or rise in feet per 

 chain for each degree or per cent of slope. This rule is based on 

 per cents of slope on a scale of 16 inches to the mile which scale 

 is to be preferred to a smaller scale in intensive mapping. 



Summary of Office Work. 

 A brief resume of the draftsman's work is as follows : — 

 I. Correction for horizontal closure. 2. Graphic calculation of 

 the elevation of slope stations and correction for vertical closure. 

 3. Obtaining elevations to one side of the line. 4. Drawing con- 

 tours in strict conformity with the form lines of the field sketch. 



These operations are all simple, and easily understood. Speed 

 will become largely a matter of practice. The correction of 

 aneroid elevations takes considerable time and value of the 

 final result is not always satisfactory. The draftsman can per- 

 form all his office work using this rule described as quickly as 

 preparing a creditable map from aneroid data. In thus using 

 graphic methods almost entirely one of the chief objections to 

 the use of the Abney is removed and the draftsman will be able 

 to meet all demands for speed made upon him in his work. 



The greater wealth of detail furnished by these Abney field 

 notes may call for more work in plotting the data supplied. The 

 practical uses however, to which a map can be put should be the 



