SCIOPTICON MANUAL. 
37 
Olt is thoroughly drained out of the lamp-cup should the 
instrument have to bo repacked for transportation by 
public conveyance. 
Standing behind the instrument, placed about breast 
high—as upon its box on a stand or table—close down 
the reflector H, pass in the slides at o o' with the right 
hand, taking them out with the left as other slides take 
their places. Focus the picture by the milled head e, 
upon the screen, which may be distant sixteen feet, 
more or less, as it is desired to have the scenes on a 
larger or smaller scale. 
k (unlike the cut) is horizontal, and turns up to give 
the appearance of a falling curtain on the screen. 
THE SCREEN. 
There can be nothing better for the projected pictures 
than the white-finished, whitewashed, or white-papered 
walls of many a lecture-room or dwelling. An appro¬ 
priate space specially set apart and papered with white 
wall paper, having an outline, say of a wide recess or 
niche for statuary, is an inexpensive and not inelegant 
fixture, on which to display before the assembled house¬ 
hold, without waste of room or trouble in arranging, the 
richest treasures of all the art galleries in Christendom. 
The time is coming, when for purposes of demonstra¬ 
tion and illustration in the lecture-room, this whiteboard 
will rival the blackboard. 
The best material in the market for a movable screen 
of good size, seems to be bleached sheeting of close 
texture, but not very fine, twelve-quarters wide. This 
gives us the material, nine feet square, for about two 
dollars. It has the advantage of being available 
whether the instrument is placed before or behind it. 
As, however, every pencil of light falling between the