I3& OPTICAL PROJECTION 



off as a square lid. The bi-unial lantern was laid down in 

 the box on its side, little compartments filling up all vacant 

 spaces between the brass fronts, &c. ; and finally the sheet, 

 folded to fit, was laid over all, and served as a soft packing to 

 keep the whole from rattling. The box was made this way 

 to allow of the sheet being thus laid on the top last of all. 



If the lantern has lengthening tubes and extra lenses, 

 precise fittings should be provided for all these ; and ' packings ' 

 should be carefully arranged, with proper cloth linings, to 

 keep the whole in place quite free from shake. A box thus 

 carefully packed is far stronger than one in which the lantern 

 is at all loose ; and as the weight of a bi-unial or tri-unial 

 is considerable, an extra sovereign spent on the cabinet is true 

 economy. It only remains to add, that the cabinet should 

 be arranged so that all the jets, dissolvers, and their rubber 

 connections may be left in place ; and that a measuring-tape 

 should by all means form part of the contents. 



CHAPTER X 



SLIDES, CARRIEES, AND EFFECTS 



74. Slides. Very little need be said about ordinary slides 

 for the exhibition lantern. They practically consist of four 

 kinds : there are plain photographs, tinted and painted photo- 

 graphs, and hand-painted slides. These latter have been in 

 so much less demand of late years, owing to the excellence of 

 the better painted photographs, that they are not easy to pro- 

 cure now-a-days ; but they are still to be had by paying for 

 them. 



Really good plain photographs are charming, and some of 

 the very best have been produced by amateurs. The main 

 thing is the extent to which the half-tones and atmospheric 



