88 
HINTS TO TRAVELLERS. 
simple route-stirvey ; 2. A district-survey; 3. A special survey of a small 
tract of country; and 4. A survey of a plot of ground containing ruins, 
&c. The only instruments supposed to be available are—sextant, watch 
or chronometer, prismatic compass, measuring tape, aneroid, &c. 
1. JRoute Surveys Arrived on the ground, the traveller must first fix, 
with as much accuracy as possible, the position of some point on the 
earth’s surface to which his work may be referred. If he starts from 
the coast-line, the position of some well-defined point can generally be 
obtained from the Admiralty Charts, but if no such resource is available, 
the position of his initial point must be determined by astronomical 
observations. The latitude can be obtained by a good observer with a 
6-inch sextant to about 100 yards on the earth’s surface; but the longitude 
is seldom found by lunar distances to within ten minutes (10 miles on 
the Equator). The position of the initial point, A, having been deter¬ 
mined, work commences. The true bearing of some well-defined distant 
peak, or other landmark, is obtained, and this having been made “ zero,” 
a round of angles is taken with the sextant to conspicuous objects, some of 
which should be in the direction of the proposed line of march, and, if 
possible, near the first halting-place. Several observations of the zero- 
point are made with the compass, the needle being deflected each time, to 
obtain the variation, and the aneroid read for altitude. All angles should 
be booked at once in ink, and the names of the observed objects carefully 
noted; a rough outline-sketch of the peaks or other landmarks will be 
found useful in identifying points as the work proceeds. The initial 
point, A, is pricked off on the sketching-card in a suitable position for 
laying down the day’s march, and surrounded by a circle O; the observed 
angles are plotted; and a magnetic meridian is drawn; all is then ready 
for plotting the route. The compass is set up at A, and the sights of the 
instrument are directed on some object, b' } in the direction of the line of 
march; the bearing of b' is read off and plotted from A on the field-sheet 
by means of the protractor; bearings are then taken to conspicuous objects 
such as X, which appear to lie near the line of march, and these are 
likewise plotted. The march now commences in the direction of A b', and 
is continued to the point b, where the route is found to turn to the right; 
the distance A b , measured during the march, is laid down upon the field- 
sheet, and the point b, surrounded by a circle ©; the compass is then set 
up at b } and the bearing of an object, c', in the direction of the new line of 
