324 Grubb — A Neio Collimating -Telescope Gun-Sight for large and small Ordnance. 



■would be of course equally imi)racticable for obvious i-easons, but it is instanced 

 to show that a beam of light has the necessary qualifications for our purposes. 



Now, the sight which forms the subject of this Paper attains a similar result, 

 not by projecting an actual spot of light or an image on the object, but by 

 projecting, what is called in optical language, a '■'■virtual'''' image upon it. 



Dksckiption. 



The original conception of this sight is represented in fig. 1. The object to 

 be aimed at is viewed through a short piece of tube (4i>) preferably square, 



A- 



^^ 1^ 



open at both cuds, in wliich is mounted, at an angle of 45°, a plate or plates 

 of parallel glass, similar to tliose used in sextants. 



