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AUTO-SIGHTING. 
- BY - 
COLONEL SIR G. S. CLARKE, K.C.M.G., F.R.S., R.E. 
I N the “ Proceedings” of the R.A. Institution, for June, 1898, Colonel 
H. S. S. Watkin, c.b., gives a most lucid explanation of the princi¬ 
ples involved in auto-sighting, and provides diagrams showing two part¬ 
ial solutions of the problem. That problem may be shortly defined as 
follows:— 
Given the height of the gun above the sea-level at any moment, the 
angle of depression of the line of sight evidently determines the range. 
It is required, by mechanical arrangements connecting the line of 
sight with the gun, to ensure that when the former is laid on the water¬ 
line of any floating target, the latter shall automatically take up the 
quadrant elevation corresponding to the range. As the tail cannot 
wag the dog, so the sight must be moved by the gun, the latter being 
elevated or depressed till the former comes u on” with the target. 
Such are the theoretical conditions to be fulfilled; but subsidiary 
difficulties are involved. It is necessary, in all cases where the rise 
and fall of tide is considerable, to provide a suitable correction. It 
is further necessary to be able to correct for the various disturbing 
causes comprehended in the term “ error of the day,” causes which 
combine to prevent the gun from shooting true to its range table. 
While I have nothing but admiration for Colonel Watkin's 
handling of the theoretical considerations appertaining to auto¬ 
sighting, I disagree absolutely with his conclusions that auto-sights 
are of use only in exceptional cases and that there is u danger 99 in 
“ supposing that they can take the place generally of the present 
methods of laying guns.” The only danger, in my opinion, is that the 
immense advantages which auto-sighting offers to the Garrison 
Artilleryman may not be adequately and promptly realized. As large 
numbers of auto-sights are in course of manufacture, it seems desirable 
to attempt to allay the misgivings to which Colonel Watkin’s able 
paper must evidently give rise. 
His forebodings are based upon the two following objections:— 
1. The errors of observation are so great that accuracy cannot 
be expected. 
2. The “ serious errors 99 due to eccentricities on the part of 
the “ racers 99 will suffice to vitiate auto-sighting even if 
(1) could be eliminated. 
3, VOL, XXVI, 
