512 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



two series, a clear view of object and pencil point can be had with any 

 combination of objective and eye-piece. The prism mounting has a 

 centring arrangement, so that the aperture in the prism can be centred 

 to the Microscope eye-piece, giving a clearly defined and equally illu- 

 minated image of the object. The prism can be turned back, permitting 

 the use of the Microscope and the changing of eye-pieces without dis- 

 turbing the camera lucida. The mirror is extra large, giving large 

 drawings. The mirror bar is graduated in millimetres, and is movable, 

 so that the distance between mirror and prism may be varied to suit 

 conditions. The camera lucida is attached to the Microscope draw-tube 

 by a collar with binding screw, so that the prism can be set at the proper 

 distance from the eye-lens, as, without this adjustment, the camera 

 lucida cannot be used with all eye-pieces. 



Bausch and Lomb's Adjustable Drawing Board.* — The necessary 

 inclination of the mirror of the Abbe camera lucida to the drawing 



Fig. 108. 



surface produces a constantly increasing elongation of the visual field 

 when the drawing surface is parallel to the field of the Microscope, 

 except when the mirror of the camera lucida is at 45°. It is, therefore, 

 necessary to incline the drawing surface (fig. 108) in order to obtain 

 accurate reproductions of any considerable size. The drawing board is 

 vertically movable on a strong metal axis, to secure the same magnifica- 

 tion on the paper as in the Microscope. The drawing plane is inclined 

 by raising the right hand end of the board, a ratchet arm holding it 

 firmly in any position. The angle of inclination is read off on the 

 graduated arc. The Microscope is held in place by a clamp. 



Davis, D. J. A. — A Method of Microscopic Observation by means of Lateral 

 Illumination. Trans. Chicago Pathol. Soc, vi. (1904) p. 90. 



Dowdy, S. E.— Attachable Object-finder. 



English Mechanic, lxxix. (1904) p. 410. 



Catalogue A, 1904 (Microscopes and Accessory Apparatus) p. 70. 



