C is the constant, or ratio, to be found for each instrument. 



' d sin I" 



Substitute the value of d from the first equation, and the formula 

 becomes: 



HR 



B -- 1 ft., colotr. -. .00000 



H = 100ft., log. 2.00000 

 R = 608.33 ft., Ing. = 2.78414 

 C = Constant, log. 4.78414, 

 By transposition in the last equation we have 



60833 



Example : Base, or B, = 6 ft. 



Divisions on the head, or R, = 365. 

 Find the distance from the base, or H. 



H =* = 6 X !? 833 - = 999.999 ft., or 1000 ft. 



When the instrument is used for running lines of comparatively 

 short sights, a table similar to the following, computed for each 

 instrument, may be used. 



BASES 



The figures 1, 2, 3, etc., shown at the head of th table, are the 

 length, in feet, of bases which are used, either upon a stadia rod or 

 established upon the ground. In the left hand column, the quantities 

 are lOOths. of a mile. The figures in the body of the table repre- 

 sent the number of divisions read on the micrometer head. In ex- 

 planation of the use of the table, let us suppose that a base of 5 ft. 

 has been used and 254 divisions have been recorded from the 

 micrometer head. Following down the column headed 5, the 

 nearest figure to 254 is 256. By following this line to the left we 

 find that 0.23 miles is the distance. If a closer determination is re- 

 quired, it may be found by interpolation. For longer distances and 



M 



