46 H. L. Smith on a new Binocular Eye-piece. 
is placed with its reflecting face parallel, but slightly inclined 
to the face of the plate a6 ; the proper position is determined 
to suit the ordinary varying distance of the eyes. It is obvi- 
ous, that in the construction, fig. 2, the di he 
eyes may be allowed for, without sliding out the eye-piece by _ 
changing tubes and rotating the 
