CAM′ERA LU′CIDA

[L. and Eng.] When a ray of light ( r ) falls upon a quadrangular gla prism ( a ), it is bent by two reflections (at c and d ), and thrown upwards where it may be received by the eye, to which it will appear described on the table or sheet of paper ( f ) placed to receive it. The point of a pencil used to trace any object on the paper can also be seen, and by its means the picture can be easily copied. When the prism is mounted on a stand, and a thin bra plate with a small hole through it for the eyepiece adjusted thereto, it forms the CAMERA LUCIDA of the opticians. The image may be magnified or le ened by placing a lens so as either to intercept the rays before they strike the prism, or before they reach the eye. An ingenious person will readily be able to set up this instrument, than which a more useful one cannot exist. IMG:596405606043057898_i403-1.png: