the instrumental constant for any angle, as determined by the 

 stadia tables, is to be finally added if the accuracy attempted re- 

 quires that the constant be considered at all. 



The Beaman 3- Stadia Arc 



as applied to the Standard Alidade 

 Fix- 65 



The H-Scale is used for the rapid reduction of horizontal dis- 

 tances, from the observed inclined distance, as determined from the 

 rod interval and the instrumental constant. This is a second set of 

 graduations representing certain angular values that correspond to 

 those in the reduction table on page 116. Obviously there will be 

 definite angles of inclination in which the base can be determined 

 directly by substracting from a hypothetical hypothenuse, a certain 

 percentage of itself; thus, if the telescope is inclined at 18 26' ami 

 the uncorrected stadia interval read 7.2 (or 720 ft. inclined distance) 

 \%e know that the horizontal equivalent is to be determined at once 

 by substracting from this imaginary distance, 10 $> of itself or 72 ft., 

 leaxing 648 ft. as the correct horizontal distance to the anterior 

 focal point. 



The V-Scale and the H-Scale do not correspond precisely but 

 when the V- Scale has been set to some even multiple, as explained, 

 the graduations of the H-Scale will suggest the approximate if not 

 the actual percentage by which the Inclined distance is to be re 

 duced. If necessary, slightly change the inclination of the telescope 

 to correspond with one of the angular values given in the tables, 

 then substract the corresponding percentage from K times the rod 

 interval. 



