18 A MANUAL FOR NORTHERN WOODSMEN 
wider use, is stadia measurement, or the measurement of 
distance by wires placed in the focus of a telescope and 
the space which they cut off on a graduated rod. The 
principles of this method are stated on page 77. 
For this purpose a light telescope may be fitted to 
the rear sight of the compass, as shown in the illustra¬ 
tion, a level and vertical 
circle being added if the 
instrument is to be used 
on rough ground. The 
cost of such an instrument 
complete is about the same 
as that of a compass. Its 
adjustments will readily 
be understood from its 
construction and from 
consideration of the ad¬ 
justments required for the 
transit. 
The advantages of this 
instrument in land sur¬ 
veying are as follows: — 
1. Sights may be taken 
on steeper ground, either 
up or down hill, than can 
be covered through com¬ 
pass sights. 
2. Distances over very, 
steep ground can be 
measured more accurately 
and quickly than by use 
of the chain. 
3. Distance across 
gorges, swamps, and bodies of water can be obtained 
directly and with ease. 
4. It enables the surveyor himself to perform all the 
particular work on a survey, and this on short jobs, or 
wherever reliable chainmen cannot be had, may be a very 
great advantage. 
Stadia wires in an instrument used for land surveying 
