26 Sir David Brewster on a Binocular Camera, §c. 



If we now wish, by directing the "axes of the eyes beyond MN 

 to b, to ascertain the value of Cc', which will give different depths 

 d of the hollow solids corresponding to different values of Cb, we 



shall have Kb : -^ —d:Cc' and Cc' = jr-rj? ; which, making AC8 



inches as before, will give the following results : — 

 Depth. 



The values of h and d, when the excentricities Cc, Cc', as 

 we may call them, are known, will be found by the formulae 



h= ^-t-tt and d= =r-r-=-. As Cc is always equal to Cc' in each 

 2AB 2A.b 



pair of figures or dissimilar pictures, the depth of the ho/low solid 



will always appear much greater than the height of the raised 



solid one. When Cc and Cc' are both 0'75 h:d=S : 12, and 



when they are both 0-4166, h : d=2 : 4, and when they are both 



0139A:rf=0'8:10. 



III. Account of a Binocular Camera, and of a Method of ob- 

 taining Drawings of Full Length and Colossal Statues, and of 

 Living Bodies, ivhich can be exhibited as Solids by the Ste- 

 reoscope. By Sir David Brewster,, K.H., D.C.L., F.R.S., 

 and V.P.R.S. Edin.* 



IN explaining the construction and use of the lenticular and 

 other stereoscopes, I have referred only to the duplication 

 and union of the dissimilar drawings on a plane of geometrical and 

 symmetrical solids. The most interesting application, however, of 

 these instruments is to the dissimilar representations of statues 

 and living bodies of all sizes and forms, and also to natural 

 scenery, and the objects which enter into its composition. Professor 



* From Trans, of Royal Scottish Society of Arts, 1849. See also Report 

 of British Association at Birmingham, 1849, Trans, of Sect., p. 5. 



