6 A MANUAL FOR NORTHERN WOODSMEN 



line some feet away, and then look through the sights upon 

 it. If the plumb line appears to traverse the forward slit 

 exactly, that sight is in adjustment. If not, file off the base 

 of the sight until the adjustment does come. Then revolve 

 the compass 180 and test the other sight in the same 

 manner. 



3. KEEPING THE COMPASS IN ORDER 



Sharpening Pivot. The pivot or center pin of a compass 

 much in use is liable to become dulled so that the needle 

 does not swing freely. To obviate this the needle should 

 always be raised off the pivot when the compass is being 

 carried. A much blunted pivot should be handed over to a 

 jeweller to be turned down in a lathe, but ordinary sharp- 

 ening can readily be accomplished by the surveyor him- 

 self with the aid of a fine whetstone and the small wrench 

 usually supplied with a compass, or a pair of pliers. The 

 pivot should be removed from the compass box and fixed 

 in the end of a small, split stick; the point may then be 

 sharpened by twirling it gently on the stone at an angle of 

 about 30 with its surface. When the point is made so 

 fine and sharp as to be invisible to the eye, it should be 

 smoothed by rubbing it on the surface of a soft, clean 

 piece of leather. 



Remagnetizing Needle. Dulness of the needle may 

 be due to the fact that it has lost its magnetism and needs 

 to be recharged. For this purpose a permanent magnet is 

 required. The north end of the needle should be passed 

 several times along that pole of the magnet which attracts 

 it, and the south end passed similarly over the opposite 

 pole. The passes should be made from center to end of 

 the needle, and a circle described in bringing the two ends 

 successively into contact. In order to prevent the loss of 

 magnetism, the needle of a compass not in use for a con- 

 siderable time should lie in the north and south direction. 



Balancing Needle. The needle is commonly balanced 

 on the pivot by a fine brass wire wound around the south 

 end. If change of latitude is made, the balance will be 

 destroyed, and the wire may be shifted to make adjustment. 



Replacing Glass. In case of emergency, a piece of win- 



