surveying by latitudes and azimuths. 
133 
it will intersect every parallel and meridian at the same angle, thereby 
allowing all relative bearings to be readily and correctly laid down by 
straight lines, which could not be done on a map on any of the other pro¬ 
jections in common use. A fter having prepared his projection, a reference 
to the annexed map, facing p. 134, will show the traveller how he should 
proceed. 
The first thing to do is to fix the position in latitude and longitude of 
the starting point A. This may be done by traverse, or bearings from some 
object, the position of which has been fixed, or by one of the methods 
mentioned in this book. Having done this, he should from the summit 
of A, look for some prominent and distant object, in the direction he is 
about to travel, such as the hill B on the map, and find its true bearing 
by measuring its angular distance from the sun by the methods shown 
(pp. 206, 207). If a sextant is used all such measurements must be 
reduced to the horizon, as shown in the example p. 206. When a transit 
theodolite is employed no such reduction Js required, and it will only be 
necessary to make the hill B his zero point, and then observe the 
altitudes of the sun, with the vertical circle face right, and face left, in 
pairs (as explained p. 27), noting the times, altitudes, and horizontal 
angles. With the times and altitudes he must compute the sun’s true 
azimuth (pp. 206, 207), and by applying the mean of the horizontal 
readings to this, he will obtain the true bearing of B. 
The next step will be to set off, indefinitely, this line of bearing from 
A, and the point B will be somewhere on that line. Having thus obtained 
the true bearing of B, the true bearing of any object in sight can be at 
once known by measuring the angular distance between it and B. Or, 
if furnished with a plane-table, regarding B as the other end of the base 
and drawing rays to each object, marking each ray in such a manner as 
to prevent any future mistakes as to the object through which the ray is 
drawn. 
We will now suppose that the traveller proceeds in the direction 
indicated on the map, meeting with obstacles which prevent his keeping 
in a direct line towards B, and that he allows his watch to run down, 
thus losing his Greenwich time, or the time of such other place as he has 
chosen for his reference meridian, and that after several days’ march he 
finds himself in the vicinity of B. There he will have an opportunity of 
fixing the position of B, finding the error of his watch on his reference 
