242 
A Pocket Mapping Instrument — Lane. 
that number in the first cohiran (of the table below) which is 
in the same horizontal row with the chosen course, we can 
easily plat it from some chosen point, and thus continue. 
Several sheets of coordinate paper are always kept in the frame 
in case our course should lead us off the first one. At each 
stop we can fill in the topography accurately as the sheet and 
the country lie before us in the same position. 
TABLE OF COURSES. 
A run of 
on a course 
will carry 
and further 
: N. E. 
asN. 
E. : 
103.+.07 
140 +3' 
100 
25 
76°- 3' 
316.+.20 
180+25' 
300 
100 
720-25' 
112. -.20 
27°-26' 
100 
50 
620+26' 
360. +.53 
34O-I9' 
300 
200 
560+19' 
125. -.00 
370- S' 
100 
75 
530- 8' 
141. +.42 
450 
100 
100 
450 
Paces. 
: E. 
N. 
N.E. : 
This table should be memorized or written on the back of 
the geograph. 
Or secondly it may be used as a plane table, a strip of stiff 
colored card with a graduated edge or even a pencil, serving 
for an alidade. Point the card in the direction to be deter- 
mined (keeping the side of the geograph pointing N.) and 
draw a line along it. 
There are some other incidental points. If you have your 
maps cut up and mounted on linen to fit, they may be slipped 
in. It will save wear and dirt and enable you to orient your 
map in a moment. Moreover you can keep your course on 
the map, or on a sheet of tracing linen over it in the frame. 
Whenever it is needful to make or finish a run in wet weather 
tracing linen or oiled paper can be slipped over the map or 
coordinate paper and the notes continued. It is not a bad 
idea to make blue prints of maps for field work and for this 
the frame is useful. 
Thinking that this geograph might be of use professionally 
to others than geologists, — woodsmen, explorers, prospectors, 
army engineers, etc., I have taken steps to have it patented. 
But if any geologist will order one from me specifying how he 
