LENGTH OF A SHAFT OR ADIT. 



137 



irregular, 



such as in 



Should the hill-side A c E G be 

 Figure 66. 



Then A c, c E, E G, should be measured from convenient 

 points, A, C, E, G. To find the length of shaft A o, find the 

 lengths of A B, c D, E F, as in the last example. The whole 

 length A equals the sum of the lengths A B, C D, E F. 



In the same way, the length of the adit O G equals the 

 sum of the lengths B c, D E, F G. 



Also, if any two sides of the right-angled triangle ABC are 

 known, the third side can also be found without using the 

 Table of Sines. 



FIG. 66. 



FIG.66A. 



For A c = square root of (A B 2 + B c 2 ) 



A B = (A C 2 - B C 2 ) 



(AC 2 -AB 2 ) 











Thus, supposing AC = 100 feet, 

 A B = 80 feet, 



B c would equal the square root of 100 x 100 - 80 X 80, 

 that is, square root of 3600, that is, 60 feet. 



If it is required to know how deep a shaft will have to 



