On an Imjproved Finder. By W. Webb. 753 



It is not uncommonly supposed that it is impossible to use a 

 finder unless with a movable stage and a stop, but in the absence 

 of these it is simply necessary to place the thumb, or a finger of 

 the right hand, upon the slip of glass carrying the object (when it 

 is in the centre of the field) to prevent it moving, and then to place 

 the thumb-nail of the left hand, or another slip of glass, against the 

 left-hand edge of the object-slip, and hold it there while the object 

 is taken ofi" the stage and a finder is put in its place against the 

 thumb-nail or shp, and read off as above explained, and the 

 number of the squares recorded. 



The finder will also be found very useful as a stage-plate for 

 the draughtsman with the camera lucida. 



If ruled upon disks for the eye-piece they are unique, as the 

 plotting and the object are seen as one, either with or without the 

 camera lucida or neutral tint glass. 



The finders are all ruled and mounted so mathematically alike 

 as to enable a slide to be marked and sent to any part of the world 

 wherever a Webb's finder may be. 



VOT., Tir. 



