SLIDES, CARRIERS, AND EFFECTS 145 



light upon the screen, interlacing with one another, and due 

 to the persistence of vision. Beale's Choreutoscope rapidly 

 substitutes different attitudes of the same figure, and thus 

 gives the effect of motion, a favourite subject being a dancing 

 skeleton ; but this effect is better rendered by an apparatus 

 used by Mr. Muybridge, in which the figures are rotated, 

 whilst the Choreutoscope draws them along in a straight 

 line. 



A simple application of the pantograph has produced a 

 lantern sketcher, which in clever hands is very attractive, 

 sketching out a design upon the screen ; and there is also an 

 ingenious slide called the Cycloidotrope, sold at 80s., which 

 by a combination of mechanism produces upon the screen, 

 cutting them through smoked glass with a tracing point, 

 most beautiful geometrical patterns of cycloidal curves. Real 

 experiments belong to the latter portion of this work. 



CHAPTER XI 



ACCESSORY INSTRUMENTS 



SEVERAL instruments are frequently used with ordinary 

 exhibition lanterns for public entertainment, which demand 

 a few words before proceeding to the scientific class of pro- 

 jections. 



79. The Kaleidoscope. This beautiful invention of Sir 

 David Brewster for showing the symmetrical effects of multiple 

 reflection, was adapted to the lantern by the late Mr. J. Darker. 

 As is well known, two mirrors have to be fixed so as to meet 

 at an angle which shall be an aliquot part of a circle. They 

 are fixed in a tube as at A (fig. 76), and the effect is that 

 the phenomena between them are repeated symmetrically all 



