Gkubb — A Neiv CoUimalin^- Telescope Gun- Sight for large and small Ordnance. 823 



the old, admittedly defective, naked-eye sights. This has been attributed to 

 various causes : — 



(«) The limited field of view rendering it more difficult to catch up the object. 



(h) The greater apparent speed of the moving objects, owing to the magnifica- 

 tion, and consequent difficulty of aiming at them. 



(c) The parallax errors produced by imperfect focussing, and the difficulty 

 of providing a telescope which will keep in adjustment, notwithstanding 

 the concussions to which it is subject. This difficulty is so serious that 

 arrangements are generally made for removing the telescope before 

 each explosion. 



((/) The unpleasantness, not to say the danger of keeping the eye against an 

 eye-stop while firing the gun, and many other like reasons, probably the 

 greatest being that, the eye being fixed to the eye-piece, one loses 

 cognizance of everything that goes on around except wliat can be seen 

 in the limited field of the telescope, and thus valuable opportunities 

 may be lost. 



If possible, there should be no obstruction to the view, so that advantage may 

 be taken of any puif of smoke or other indication of the enemy's whereabouts. 



To return, however, to the ordinary or non-telescopic sights. The difficulties 

 consist in the matching or superposing three objects on one another, any two 

 of which must be indistinct when the eye is focussed on the third ; and of avoiding 

 parallax due to want of precision in position of the eye. 



To find some contrivance for the purpose of obviating these difficulties i.s the 

 problem that jH'esents itself. 



An ideal sighting arrangement, though of course an absolutely impracticable 

 one, might be conceived, as consisting of a ring or cross supported on an 

 immensely long rod giving a prolongation to the gun-barrel, the rod being 

 absolutely imponderable and perfectly stiff, so that the ring or cross would 

 always be carried precisely in the prolongation of the axis, and every shot fired 

 would pass through the ring. Now if the rod be only long enough to reach to 

 the object, we have evidently merely to place this ring on the object and the shot 

 must liit, as it must pass through the ring, and in this case there is plainly no 

 necessity for any back-sight. But, it may be said, no such rod or beam is 

 obtainable that would be absolutely imponderable and perfectly free from 

 flexure. There is one exception to this, and that is a beam of light. 



It would be possible to conceive an arrangement by which a fine beam of light 

 like that from a search-light would be projected from a gun in the direction of its 

 axis, and so adjusted as to correspond with the line of fire, so that, wherever the 

 beam of light impinged upon an object, the shot would hit. This arrangement 



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