28 SCIOPTIOON MANUAL. 



Bafer. A lantern with a calcium light of either kind is 

 commonly called a Stereopticon. 



The Magnesium light is excellent in photography, but 

 it gives off troublesome fumes, and for a continued 

 lantern exhibition is too liable, even with well-regulated 

 clockwork, to leave the lookers-on in sudden darkness. 



The Electric light is intense and concentrated, but it 

 requires too much apparatus to be available. 



The above so-called chemical lights, are, if well man- 

 aged, much brighter than flame, even at its best. The 

 Sciopticon has a double flame, which is not only very 

 bright, but gives much more distinctness to the image, 

 by its standing edgewise to the condenser instead of 

 broadside, as a single flame must, to prevent its casting 

 a dark shadow on the disk. No lantern of any sort can 

 compare with the Sciopticon in point of convenience. 

 We may conclude that the Hydro-Oxy-Calcium light is 

 best for exhibitions on a large scale, and as for the rest, 

 the Sciopticon is desirable as combining efficiency and 

 great convenience. 



THE SIZE PROPER FOR THE ILLUMINATED DISK. 



The image enlarges in area, and diminishes propor- 

 tionately in brightness, as the distance of the lantern 

 from the screen increases. A disk of six or seven feet 

 is about right for figures, statuary, <fcc., to give bright- 

 ness and not an unnatural size ; while landscapes, &c., 

 appear better on a disk of eight or ten feet, or more. 

 With an objective of about four inches back focus, as is 

 most used on the Sciopticon, a distance of about sixteen 

 feet from the screen gives a disk of about eight feet. 

 The arrangement can be varied to suit circumstances. 



