CH. VI] 



HELIOSTATS FOR THE MAGIC LANTERN 



141 



ported by a framework. This frame should be hinged so that it 

 can be moved from the horizontal up to the vertical position. It 

 must also be so mounted that it can be rotated around at right 

 angles to the hinge motion. 



FlG. 75. PORTE-LUMIKRE WITH PLANO-CONVEX LENS AND PROJECTION 



OBJECTIVE. 

 (Cut loaned by the C. II. Stoelting Co.}. 



The mirror for the reflection of the sunlight into the condenser is moved as 

 necessary by the milled head just above the condenser. 



The two movements arc made by hand as often as needed while 

 one is using the apparatus. In the original forms of Cuff and 

 Adams (1744-1746, fig. /5a), and in some modern forms, there are 

 two handles or milled heads extending into the projection room; 

 with one of them the operator can raise or lower the mirror on its 

 hinges, and by the other he can rotate it on the other axis. In the 

 form here shown there is but one handle. This serves as a crank 



