APPENDIX 



43? 



and a simple lever converges the three images into one harmonious 

 whole (fig. 247). 



The effect, as the three crude and almost painfully glaring 

 coloured images are resolved into one, and an artistically coloured 

 picture suddenly springs into life, as it were, is an extremely 

 pleasing one, and the instrument as now manufactured by 

 Messrs. Newton & Co. forms a most useful addition to a lecturer's 

 outfit. As all the parts, colour screens, mirrors, &c., are removable, 

 the principle of the three so-called primary colours, and their 



FIG. 247. Ives' Photochromoscope 



combination in the final picture, can be demonstrated step by step. 

 When no slide is placed in the stage the appearance on the screen 

 is that of three coloured discs producing white as they gradually 

 converge and overlap, and if then a obstacle, such as the blade of 

 a penknife, is placed in one of the stages, the shadow on the screen 

 will have the complementary colour, composed of the union of the 

 remaining two coloured discs. 



A good series of slides for this instrument is now obtainable, or, 

 by means of a special dark slide which can be fitted to any good 

 camera, amateurs can prepare their own subjects. An instrument 

 for viewing these slides, instead of projecting them on the screen, is 

 also obtainable, but a description of it hardly belongs to these 

 pages. Objects for this latter instrument may be stereoscopic, as 

 the arrangement is binocular. 



