782 REPORT— 1903. 



4, Further Experiences with the Infantry Range-finder. 

 By Professor George Forbes, F.R.S. 



This paper deals with the facility of learning to use the range-finder, its 

 employment with artillery, and its accuracy in tlie hands of men selected with 

 good eyesight. 



In 1901 the author exhibited to the British Association his portable steneo- 

 scopic infantry range-finder, and gave the results of trials to test its accuracy. 



To test its durability in the field, the author used it in the South African war, 

 with Colonel Crabbe's column, under General Sir John French, and the reports 

 upon its accuracy and durability in the field were certainly satisfactory. The 

 results obtained in actual war and under fire were given to the Association at the 

 last meeting. 



The only point remaining to be established, in order to prove its entire suita- 

 bility for infautrj-, is the facility of learning its use, some people having a 

 suspicion that the steneoscopic effect would not be obtained by a large proportion 

 of ordinary men. The following results show that out of over fifty men who gave 

 the range-finder a trial of five minutes, not one failed to take ranges with con- 

 siderable accuracy, and only one was not sufficiently interested to give the five 

 minutes' necessary attention to it. 



These trials took place at Aldershot under a War Office Committee, and at 

 Bisley under the auspices of the National Hifle Association. In the former case 

 three sei^geants and five privates were chosen haphazard for instruction ; and, 

 although the weather was most unsuitable, not one of them failed, and the 

 progress made by all of them was most satisfactory. At the Bisley trials forty- 

 one men took instruction, and all — with the single exception already mentioned 

 — were able within half an hour to take easy ranges with accuracy ; while fifteen 

 of them presented themselves for a prize competition in its use. The results 

 obtained by the winners of the first two prizes at five distances chosen, up to 

 1,G70 yards, were: Sergeant F. E. Pollard had an average error of 10'8 yards, 

 or I'l per cent, of the average distance ; and his average time for an observation 

 was 12 seconds. Colonel Milner's average error was 11'4 yards, or 1'2 per 

 cent, of the average distance ; and his average time for an observation was 

 14'5 seconds. It is worthy of note that not one of the competitors had previously 

 received more than one hour's instruction or practice, while Sergeant Pollard, the 

 winner of the first prize, had never seen the instrument until about half an hour 

 before he actually competed. 



Experiments were made with the infantry range-finder in July 1903 on 

 Salisbury Plain with artillery. The object sought was to correct for the error of 

 the day, including variations in ammunition and weather, more quickly than is 

 possible by the existing system of bracketing by firing the first shot with shrapnel 

 which bursts in the air, taking the range of this burst — which is seen as a white 

 cloud — and making the necessary correction for the second shot, which would 

 then be on the target. The results obtained at two ranges are as follows, the 

 distance short or over, as found by the range-finder, being first given, and theu 

 the same distance as estimated by the range-party near the target, for each 

 shot : 



I. Range, 2,840 yards— (1) 200 short, loO short ; (2) 100 short, 200 short ; 

 (3) 120 short, 170 short ; (4) 200 short, 210 short; (5) 150 short, 160 short; 

 (6) 100 short, 110 short ; (7) 60 short, 60 short. 



II. Range, 3,535 yards— (1) 250 short, 150 short; (2) 350 short, 280 short; 

 (3) 100 over, 40 over ; (4) 120 short, 130 short ; (5) 200 short, 60 short ; 

 (6) 220 short, 140 short ; (7) 80 over, .30 over. 



The .above records include every shot observed both by the rangerfinder and 

 the range-party during the period referred to, and prove the importance of making 

 further use of this method. 



The great accuracy of this range-finder in the hands of men with ordinary 

 eyesight made it desirable to find out what could be done by selected men with 



