Sir John Robison's Camera Lucida. 



403 



ticularly calculated for the accurate representation of botani- 

 cal specimens, which it will render in their true proportions, 

 without trouble in adjustments. The disadvantage of the 

 limited range of this instrument is in some measure compen- 

 sated by the facility of its application and by its cheapness and 

 simplicity. — I am, clear Sir, very truly yours, 



James Tod, Esq. John RoBlSON. 



Sec. Soc. Arts. 



The figure represents a piece of thin plate-glass A D E F 

 set upright on a drawing-board by means of the wooden stand- 

 ard A B C, in a groove in which the edge of the plate is re- 

 tained by the wedges G and H.* 



To use this apparatus it is placed in front of the artist, with 

 the standard ABC towards him; the object to be copied is 

 laid on the left hand side of the plate, as at O : the head of 

 the observer being also a little to the left of the pillar, and 

 the eye directed towards the middle of the plate as at M, a 

 distinct image of the object O will be perceived as if it lay on 

 the paper at P ; and as at the same time a pencil held on the 

 right hand side of the plate will be equally visible, it may be 

 applied to trace the image at P. 



* Tho wooden standard is not fixed to the ikawing-board, and may be set 

 un it in any conycuicnt position. 



