THE ANEEOID. 



91 



of feet. The heights of all points along the line of traverse which will be 

 required in making the contour sketch should he read and written upon the 

 traverse. Every depression and elevation, road crossing, etc., should thus 

 be measured. There is, however, no necessity for reading the aneroid at 

 every station in the traverse. It will merely encumber the work with a 

 mass of useless data. 



Upon reaching a check point, comparison should be made with the indi- 

 cations of the aneroid. If the difference is considerable — i. e., more than a 

 contour interval — the error should be distributed backward along the line in 

 proportion to distance. If it is small, it may be neglected. 



Fig. 11. -Aneroid. ■ Fig. 12.— Works of the Aneroid. 



In all this work notebooks are not required, except as a convenient form 

 of carrying paper upon which to make the trifling computations required. 

 The plane-table sheets comprise all the records necessary. The work, as 

 it progresses, criticises itself by its closures in position and elevation, and, 

 wherever necessary, is revised immediately. 



ORGANIZATION OF PARTIES AND DISTRIBUTION OF WORK. 



Secondary triangulation, traversing, measuring of heights, and sketch- 

 ing are commonly carried on by one party. This consists of the chief of 

 party, who directs all the operations, and who does all the sketching; an 



