A PORTABLE MAP READER EOR 
FIELD SERVICE. 
BY 
MAJOR D. G. PRINSEP, R. A. 
H OW often at manoeuvres, field-days and such like occasions do 
officers want a quick and handy instrument either for finding 
their position or orienting a map or again measuring ranges from 
one point to another and how vexatious is this at times with a high 
wind and a map with the scale torn off or put in a corner where it is 
not readily to be used and with rain or snow perhaps fast reducing 
the whole thing into a blurred mass of pulp—and think of the lan¬ 
guage too that has been expended on such occasions, when your fingers 
are numb and your horse wont stand steady and an irritable umpire, 
cold and in a hurry, wants to know where you are on the map and 
what range you were firing at or are going to open fire at etc., etc. 
Well occasions such as these induced me to evolve an instrument which, 
after 2| years of trial, I can confidently assert gives one all the in¬ 
formation most urgently required on the field and it can be used 
mounted or dismounted with the greatest ease. 
The instrument* consists of a stout piece of boxwood -J inch thick 
with both edges bevelled, about 5J inches long and 1 \ inches wide ; 
on the bevelled edges are cut scales of yards to two inches to 1 mile on 
one* side and three inches to 1 mile on the other and by following the 
written instructions on the top of the scale maps of 1, 2, 3, 4 or 6 
inches to the mile can be read at once. 
On the reverse side are two scales of inches and tenths, and inches and 
eighths, while in the centre I had the fuze scale for the gun I was 
using pasted on and varnished, but this might I think be printed on a 
removable slip of wood if preferred. Anyhow it is better than the india- 
rubber range card for working with as it has no information which is 
not material for a battery commander to fight his battery with. In 
the centre is inserted a good compass needle moving in an oblong 
brass box and glass covered and at the N. and S. ends are marked 
small variation scales of degrees in the box. 
* A Diagram of the map reader may be seen at the Institution or sent by post on application for 
inspection and return. 
7. VOL . XXVI. 
