THE SURVEYOR’S COMPASS 
the compass to any given object referred to the meridian. 
It is read as so many degrees from the N or S direction, 
up to 90°; as, N 10° W, S 88° 15' E. The graduations on 
a surveyor’s compass are commonly in half degrees, but it 
is usual, if necessary, to set by estimation quarter degree, 
or 15', courses. A bearing can be set, however, with a 
surveyor’s compass in first-class order, to about 5'. 
A compass needle that is in good working order 
takes some little time to settle, and its condition may be 
told by the freedom and activity with which it moves. 
Time can be saved in setting it by checking its motion 
with the lifting screw. In its final settlement, however, 
it must be left free. For important bearings, it is well to 
let it settle two or more times independently. 
A glass plate covers the compass box and two small 
levels placed at right angles to each other are used to set 
the instrument in the horizontal plane. It is very de¬ 
sirable that the box of a compass employed for woods 
work should be as nearly watertight as possible. In 
general make-up, the instrument is subject to considerable 
variation. 
The plate of the Plain Surveyor’s Compass is prolonged 
in the north and south direction into arms on which the 
sights are supported at a distance of twelve to sixteen 
inches apart. The actual sighting is done through fine 
vertical slits, and round apertures placed at intervals along 
these are convenient for finding objects and for getting the 
instrument approximately in line. 
The Vernier Compass has the circle and the sights 
upon separate plates which may be turned on one another 
for 20° or more. Its advantage consists in the fact that 
declination, or a change in declination, may be set off, 
and the courses of an old survey set directly, or lines re¬ 
ferred to the true rather than the magnetic meridian. 
The Folding-Sight Compass possesses the advan¬ 
tages of light weight and the utmost compactness, and is 
therefore popular among woodsmen. The sights are set 
upon the edge of the compass box, and fold down across 
its face when not in use, the whole instrument with its 
mountings slipping into a leather case which may readily 
