41 
THE WELDON RANGE-FINDER. 
BY 
MAJOR J. B. RICHARDSON, R.A. 
The use of range-finders in scientific warfare is recognised as a 
necessity by nearly all the military powers; but hitherto no satis¬ 
factory instrument has been forthcoming. 
To many a hard-working battery officer who has toiled wearily 
on, instructing men in the art of range-finding with the highly- 
complicated instruments adopted in our service, happy if, by chance, 
he has succeeded in training, after hours and hours of instruction, 
say one N.C. officer in his division to find ranges accurately enough 
for the result to be depended on, the news that an instrument has 
been invented simple enough for an uneducated man to work effec¬ 
tively will be most welcome. 
Such a system of range-finding has been perfected by Major Weldon, 
of the Madras Staff Corps. It may be taught to an intelligent man in 
an hour, and to men of poor education—the class with which one 
mostly has to deal—in from three to four hours. The instrument 
used is extremely simple, devoid of calculators, verniers, cylinders, 
screws, springs, racks, or anything likely to get out of order; extremely 
portable, and so cheap that every N.C. officer might possess one, and 
carry it in his pocket. By this system a range may be found in the 
time that it takes to dismount and put a Nolan's instrument together, or 
while with a Watkin's the horses are being knee-haltered and the 
pickets being planted; and the ranges found can be depended upon. 
All range-finders depend for the accuracy of result on the length of 
the base. When the base subtends an angle of less than 2° the result is 
unreliable, unless instruments are used far too delicate for rough service 
work. Again, if the angle subtended by the base is greater than 3°, 
the base is unnecessarily long. In all range-finders worked with an 
arbitrary base the error increases with the distance; Major Weldon's 
system secures unvarying reliability at all ranges, by making the base 
