10 FIELD GEOLOGY. 



at the number of degrees corresponding with that read 

 off in the compass and a line drawn through this point 

 and the object gives the first bearing. A second line is 

 then found to cross the first, the nearer the angle be- 

 tween them is to a right angle the greater the accuracy 

 of the result. 



Note. As the protractor represents but one half 

 of the circle it will be necessary when the number 

 of degrees read off exceeds 180 (the total shewn 

 thereon) to plot that number and begin again or, 

 what is the same thing, to deduct 180 from the 

 degrees indicated and commence from the other 

 end, that is, with the protractor placed on the left- 

 hand side of the object. 



It sometimes occurs that one bearing is sufficient for 

 the purpose : e.g. when the spot is situated someivhere 

 on a road or fence-line shewn on the map, but with 

 nothing to shew its more exact position. Another and 

 a ready method of spotting one's locality where there is 

 no lack of known landmarks is to place on the ground 

 a stick, or a hammer, directed to an object ; then to 

 look along the stick from its other end and note the 

 object with which, or near to which, it is in line. This 

 gives a fair bearing in one direction, and if it be crossed 

 by another, as with the compass, the position found on 

 the map is not far wrong. 



Hammer, Pick, Spud, &c. To draw a geological 

 line, it is necessary to have at hand some means of 

 ascertaining what strata run up to the surface in any 

 locality that is to be geologically mapped. There is 

 always with very rare exceptions a depth of surface 

 soil varying from 2 or 3 inches to 2 feet or even more, 



