16 



Sir D. Brewster on New Stereoscopes. 



percentage quantity of carmine present being estimated from a 

 mixture of white and red of the same brightness. 



The chemical action of the light attains its maximum a little 



6 I ot the atoosphef through the condensation of vapours, 

 3encflnSent localiS may exhibit small variations : 

 ?W depend upon the distribution of the relative moisture} at 

 SffeLnt P eTettLs,-a subject which has been already treated of. 

 [To be continued.] 



Description of several New and Simple Stereoscopes for exM- 



n W^Z solid, one or more «£ ^f^TvPRS. 

 By Sir David Brewster,/^., D.C.L.,F.K.S., and V.r.n.z. 



EdiU ' % [With a Plate.] 



rf^HE ingenious stereoscope, invented by Prof. Wheatsioue 

 Tfoi representing solid figures by the union of dissmnlar 



"HX^ad occasion to make numerous experiments on this 



* Asie Central, Mahlmann's edition, vol. ii. p. 76. 



t See Physical Geography of the Alps, Pj^^- . f Arts> 1849 . 

 % From the Transactions .of the Royal ^^^^UsS Trans. 

 See also the Report of the British Association at Birmingham, i« 



*tnl&m. 1838,p.3 7 l. II BM- vol- xv.part3,p.360. 



