ON THE CAMERA LUCIDA. 



149 



images will not be in the least shifted from their places on 

 the paper, which is a great advantage belonging to this in- 

 strument. 



A much more important advantage peculiar to the ca- Peculiar ad- 



mera lucida is the essential benefit a young artist, may de- vanta £ e °* . l " e 



,.'.■■•■, o- -n • • camera lucida 



rive from a limited use of it. r or instance, to have the out- to the student, 



line of one or two objects, situate near the middle of the 

 view, as reflected by the prism : and afterwards to look di- 

 rectly at the view itself, using the upper edge of the prism 

 as a guide for the point of observation. His eye and judg- 

 ment may then be exercised in determining, by this outline, 

 the relative magnitudes and distances of the remaining ob- 

 jects; occasionally referring to the reflection of them in the 

 prism for their true situations in comparison with those his 

 judgment has assigned them: and these corrections, atten- 

 tively observed, seem capable of affording the most valuable 

 aid in cultivating a delicacy of discrimination. The finish- arid to the 

 ed artist will also find a great economy of time, upon ex- a 1S ' 

 tensive and complicated subjects in particular, by using the 

 instrument in determining the situations of so many points 

 as he may deem important;' and which the camera lucida is 

 allowed to give " with perfect truth and correctness of per- 

 spective." 



Though hitherto omitted, it is proper to notice the fre- View obstruct. 



quent impediments to an extent of view, arising from the et j ^> r ,heb,hn 



. . . ,. ^ „ , . , , of the hat Ac. 



projection or near objects ; parts or the heaa-dress in par- 

 ticular are sometimes unsuspected obstructions, and the 

 brim .of the hat the most formidable of all. 



Dr. Wollastou has briefly ad.verted to the method of en- An object nay 



lareing a drawing, or delineating minute objects as magni- Dedrawn ""'Sg- 

 _ °' f ,• . . 5 -, . ° . . ..-*?, nifiedbythe 



ned ; by bringing the eye piece to a vertical position and camera lucidau 



looting directly at the object through the eye-hole and the 



lens, which must be turned up likewise to the same position; 



the paper and pencil then appear reflected in front of the 



object, more or less distinctly, according t,o the quantity of 



prism exposed to the pupil : and a delineation of the object 



may be obtained large in proportion to the magnifying 



power of the glass and the surface of the paper occupied. 



To this 1 beg to add, that a compound microscope may be a compound 



used in the same manner, but more conveniently with the micro-cope 



may be used 

 horizontal 



