840 
PORTABLE MAP READER. 
I have found this a strong instrument and one that will hear being 
knocked about and can be carried in wallets, or pocket of serge or 
elsewhere, easy to handle and absolutely accurate while its thickness 
makes it easy to handle quickly even with gloves on and one has not 
got to fumble about to find a pencil first and then a piece of paper to 
measure off a distance on a map. The length gives a good line for 
orienting a map and the scales mentioned will cover all maps likely to 
be found in English countries. For foreign maps all that is necessary 
is to paste the scale of the map to be used on one of the bevelled edges. 
Messrs. Cary, Opticians, Pall Mall, London, made the first one to my 
design and will doubtless be pleased to make others for anyone re¬ 
quiring them. I have found it particularly useful for ranging a battery, 
etc., as by putting your thumb or finger across the last range given 
you know exactly where you are—and I hope others may find it as 
useful as I have. 
