CAMERA LUCIDA. 



23 



matism, necessitating the use of spectacles, render the use of the 

 camera lucida inconvenient, if not well-nigh impossible. 



Some time since it occurred to the writer that the practice of 

 micrography could be greatly simplified by adapting the principles 

 employed in ordinary projection, as used in connection with the 

 optical lantern, the projection microscope, photo-micrography, etc. 

 It was only a question of reflecting the projected image on to a 

 piece of drawing-paper fixed in some convenient position. To 

 this end I requested Messrs. Bausch and Lamb to mount a right- 

 angled, reflecting prism with a short tube extending from one of its 

 square faces, (Fig. 4), this tube to be of such calibre that it could be 

 inserted into the microscope in the place of the eye-piece. From 

 the other square face a similar short tube extends, capable of 

 receiving the ocular and holding it firmly. 



Fig. 5. — Showing lamp, microscope, and prism in position. 



When preparing to use this device the object is placed on the 

 stage, and focussed in the usual manner. The microscope is then 

 brought to a horizontal position, the eye-piece is removed, and the 

 prism case put in its place, the ocular being inserted in the short 

 tube provided for its reception. The ocular should point down- 

 ward. The lamp, or other source of light, should then be disposed 

 in such a way that it properly illuminates the object to be examined, 



