320 Gkubi? — A Ncxv ColUmuUng- Telescope Gun-Sight for large and small Ordnance. 



upon an invisible, imponderable, and inflexible prolongation of the barrel, thus 

 obviating the necessity for any back-sight, for any motion of the eye makes no 

 perceptible difference in the coincidence of this "virtual" image and the object. 

 As the form of the sight above described would evidently be highly objectionable 

 in most cases, the instrument was modified to the form shown in fig. 2, which, it 

 will be observed, is exactly on the same principle, except that instead of mounting 

 the collimating tube carrying the diphragm and object-glass, at right angles to, 

 and above, the sighting tube, this collimating tube is mounted underneath the 

 sighting tube and parallel to it, the rays being bent by a reflector or prism, 

 rendering the instrument of a more practical form. 



It will be noticed, in both this instrument and that represented by fig. 1, that 

 three plates of glass are shown superposed upon one another for reflecting the image 

 of the device on the diaphragm into the eye : — The object of this is to intensify 

 the brilliancy of the reflected image without sensibly diminishing the apparent 

 brilliancy of the object aimed it. Later on, however, it was found that a more 

 practical plan of increasing this brilliancy was to use one single piece of glass, 

 and coat this with a semi-transparent and highly i-eflective film. A long series 

 of exjjeriments carried out by Professor J. Emerson Reynolds, F.R.S., and 

 Mr. G. Rudolf Grubb, B.A.T., resulted in a modification of a process invented by 

 the former by which the desired film was obtained. 



This rvOTitixyTv s^XvarAj, 



Fig. 3. 



Fig. 3 shows a further modification, and the most generall}' favoured form of 

 instrument at the present time, in which it will be seen that the diaphragm is 



