Grussp—A New Collimating- Telescope Gun-Sight for large and small Ordnance. 323 
the old, admittedly defective, naked-eye sights. This has been attributed to 
varlous causes :— 
(a) ‘The limited field of view rendering it more difficult to catch up the object. 
(2) 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 what 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 puff 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 is the 
problem that presents 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 hit, 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 
2Y 2 
