355 
THE WELDON RANGE-FINDER. 
glass, and notes some object wbicli coincides with tbe reflection of the 
object. He then gallops on that line rather further than he believes 
the base will prove, dismounts, finds the base, and having given the 
signal “correct”—by raising his arm—paces towards No. 1, who also 
paces towards 2. They meet, add their paces, and call out the range. 
This, if the base is long, is very quick compared with the first plan— 
a base of over 100 yds. being sometimes done under the minute—but 
occasionally, as I have said, the horses check the men, particularly if 
there are many flies about. 
With the auxiliary base-finding glass the three men gallop to about 
the spot where the battery will come into action. No. 1 is angle-finder, 
No. 2 base-finder, No. 3 auxiliary base-finder. 
No. 2 proceeds as in the last, after moving some 40 yds. to front. 
Nos. 1 and 3 dismount, No. 3 gives the end of his tape to No. 1, who 
walks towards the object, 40 yds. This prevents No. 3 being so much 
hampered with his own horse. They find the range. No. 3 reads it 
off on tape, winds it up, and all three gallop in, unless the battery 
has arrived on the spot. This is very quick if all goes well, and it has 
the great advantage of allowing the battery to come into action without 
any measuring operations going on in front. But so far, chiefly I think 
owing to the inferior tapes we have to work with, it has not been a 
great success. The men dare not strain the tape, and the reel we use 
is not good for this work, it ought to be some sort of stop reel. If we 
could obtain a strong spring reel, which would wind up of itself on a 
stop being pressed, I think the auxiliary base would be a capital plan. 
We have been amused with Edwards* papers on the Weldon Eange* 
Finder. He forgets that they have been a good deal used, and were 
invented long ago. He has practically adopted Weldon's patent. His 
notion of an auxiliary base has been tried, but is quite impracticable 
from the difficulty in getting one man to align another correctly. In 
the auxiliary base used by Major Weldon, the man aligns himself. 
He asserts that such instruments as Weldon's do not measure angles 
with sufficient accuracy for an artillery range-finder, but they have 
been so used by batteries, and found sufficiently correct. Very good 
practice on very ill-defined objects has been made, and it would be well 
to make enquiries before making strong assertions. 
His description of the action of a prism is entirely new. That it is 
practically incorrect is proved by one of Major Weldon's prisms, which 
works at both ends of a base. It was, therefore, hardly worth while to 
point out that one base angle must be half the apex angle, for the 
angles of this prism are not as he describes. Perhaps there is some 
peculiar property in the prisms of Major Weldon which prevents a ray 
being deflected after the fashion of Edwards' figure, but I think if any 
