g:j the camera lucida. 14.7 



than has hitherto been done ; being persuaded, that some of i t fc as a a van . 

 these advantages are not generally known, and likewise in- ta S es not g> 

 fluenced by a wish to see 'justice done to the merit of an nepa,1 y known ' 

 invention, which deserves to be better Understood, and 

 which is peculiarly admirable for its correctness and sim- 

 plicity. 



You very justly remark, that, in using the camera lucida, Method of 

 it is certainly intended " the tracing should be made upon usin £ lt " 

 that part of the paper, where the picture and point of the 

 pencil can both be seen coincident ; and not th>* a copy 

 should be taken in the manner described by Mr. Shel-i 

 drake." But it is matter of regret, that you should not The manage- 

 have enlarged upon the effect of varying the position of the h^ot besr^* 

 eye ; in describing which the ingenious inventor im not described mi- 

 been sufficiently minute, as is strongly instanced by the nUte ? eu ® u ° '• 

 inisconception manifested in the case before us. 



Mr. Sheldrake evidently confines the camera lucida to the Mr. Shel- 

 purpose of bringing the reflection of some of the objects d 1 raI ; e " rr,e * 

 upon the upper part ot the paper, for the approximated the instrument 

 convenience of copying them upon the lower part; instead errcneous - 

 bf placing his peneil among the images themselves, and 

 " rendering them permanent," by tracing their outline at 

 Once, as himself states to be done in the camera obscura; 

 As Mr. Sheldrake seems sensible 6? the advantage of 

 moving his eye to the right and left, it is the more extra- 

 ordinary, that he should confine himself to that motion, 

 when the transverse motion Of the eye is the most obvious- 

 ly important. 



In copying a landscape the instrument is to be fixed upon Proper me- 

 a steady table or board, on which a sheet of paper is thod * 

 stretched, and the prism brought over the middle of it : the 

 bpen face of the prism is to be placed opposite the centre of 

 the view ; the black eye piece, or stop, being in a horizon- 

 tal position, is to be moved till the lucid edge of the prism 

 intersects the eye hole. The eye should now be brought 

 close to this opening, and, upon looking through it Verti- 

 cally towards the paper, a perfect copy of the view will ap. 

 pear reflected upon it, and the reflected images will be 

 large in proportion to the elevation of the prism. The eve 

 belt should now be drawn farther off the priarja,, so as to 

 L c l leave 



