138 THE PROSPECTOR'S HANDBOOK. 



be sunk, or how long an adit driven, to strike a lode whose 

 inclination to the hill-side is known, certain properties 

 belonging to any triangle and a reference to the Table of 

 Sines will suffice. Let A B c be a triangle where A c repre- 

 sents the hill-side, A B the lode, c B an adit. Let the length 

 A C be known, and also the angles a and c (and therefore 

 the angle b, which is 180 the sum of angles a and c). 

 Suppose it be required to know how far the adit will have 

 to be driven to cut the lode and also the depth of the 

 lode. 



FIG. 67. 



By a property of a triangle, 



AC X sin. a 

 Length B0 =~ ao - 



A c x sin. c 



Also, length A B = ^J~ 



The question, Where ought a shaft to be sunk 1 has to 

 be decided on as soon as development work is contem- 

 plated and though the question depends in some measure 

 on the nature of the country, rock, and other considera- 

 tions, the following general hints may be useful. 



If the lode dips in the same direction as the hill-side, the 

 shaft ought to be as in Fig. 68, A. 



If the lode dips contrary to the slope of the hill, then 

 either the shaft should be sunk on the lode or higher up 

 than the outcrop, or else below the outcrop, so that cross- 

 cuts can be driven (Fig. 68, B). 



