171 



DISCOVfaiY 



is pi '--^ibli' in a fully lighted room ; ttuTo is no luminous 

 cone, as in the case of an ordinary projection lantern 



worked in a darkened hall ; and when the projection is 

 made on a suitable screen and the images shown are 

 pictures from Art Galleries, they have all the appear- 

 ance of being the works of art themselves. 



Fig. 2 shows the apparatus when used with a folding 

 album in which picture postcards, reproductions of 

 paintings, etc., have been pasted or otherwise fixed. 

 As in the previous instance, the correct focussing on to 

 the screen is done by means of the rack and pinion 

 with which the lenses are provided. It will be seen 

 that the space underneath the portion of the lantern 

 which is lit up is sufficiently great to allow an open book 

 to be slipped under. This is of the greatest utility to 

 lecturers, who so often need to support their remarks 

 by reference to an illustration or a diagram in a work 

 of authority — an illustration or diagram which, in thr 

 case of an ordinary projection lantern, would necessitate 

 the making of a lantern slide. The multitudinous uses to 

 which the " dussaud " lends itself in this connection will 

 occur to the reader. I need mention but two or three. 

 such as scientific gatherings, lectures before military- 

 students, board meetings, demonstrations in clinics, etc. 



To project an object, say a necklace of beads, it is 



introduced into the apparatus through the door. To 

 protect the eyes of the lecturer from the intense light 

 which pours on to the object when this is done, a mobile 

 screen with a piece of dark-coloured glass in the centre 

 is hooked on to the top of the box, so that no light 

 • scapes. This enables the demonstrator to see what 

 li'- is doing. It is when the apparatus is in this form 

 ili;it it renders the utmost service to the lecturer on 

 natural history, the engineer, or commercial traveller. 

 .Natural history specimens can be introduced with the 

 greatest ease and enlarged to a size which shows their 

 anatomy, movements, colour, habits, etc., in an alto- 

 gether astonishing manner. Collectors of engravings, 

 numismatists, philatelists, jewellers, and, above all, 

 financiers will find M. Dussaud's invention of particular 

 value in this form. I may add that it was recent!}' used 

 at a great Parisian bank for the projection of bank-notes 

 and cheques, some of which were believed to be forgeries, 

 and the spurious notes or altered cheques were, thanks 

 to projection, detected with the greatest ease in the 

 presence of a number of experts. 



Fig. 3 shows the inventor holding his apparatus and 

 projecting a sketch wherever he likes : on to the 

 ceiling, on to a wall, or above a doorway. It is when 

 the apparatus is used in this manner that it will be 

 found of the greatest use to architects or artists who 

 wish to judge of the effect of a given piece of decoration, 

 say, in the corner of a room just underneath the ceiling. 

 And the effect can be judged, with all the colours of the 

 little sketch which is being projected shown, under 

 natural conditions of lighting, that is to say, in the 

 full light of day. Architects need no longer resort to 

 the stencilling of their designs, to the squaring off of 

 their drawings, to the camera lucida, to the pantograph, 

 or to other mechanical means of enlarging their sketches. 

 All that one has got to do is to project the design on to 

 the spot chosen, and then sketch it in. 



Fig. 4 represents (from left to right) the four elements 

 of which the " dussaud " is composed. On the left 

 is the box containing the lens and bearing at the top 



