20 



This consists of an approximately cubical box, the sides of which 

 are merely grooved framework in which run a set of opaque 

 roller blinds When these blinds are all drawn up, they make 

 a box with a black interior, the roller blinds being painted black 

 inside. The top of the well consists of a series of concentric 

 frames capable of carrying plain and ground glass of various 

 sizes. When it is necessary to photograph an object against a 

 black background, it is customary to lay it upon a piece of plain 

 glass, when the background, which consists of a black hole_ far 

 beyond the focus, namely the -interior of the dark-well, gives 

 an absolutely black background which is obtainable in no other 

 way. If it is necessary to secure grey backgrounds, a ground 

 glass is substituted for the plain glass and one of tbe roller 

 blinds is lowered and a mirror or other reflecting surface placed 

 in the box below. 



NATURAL SIZE DRAWINGS DIRECT. 



Another peculiar feature of the illustrator's room is a piece 

 of apparatus designed for the production of natural-size or even 

 reduced drawings with the aid of the camera lucida. 



CAMERA LUCIDA FOR NATURAL SIZE OR REDUCED 



DRAWING. 



Ever since the introduction of the camera lucida, it has been 

 more or less used for the production of natural size and reduced 

 drawings; in other words, it was soon seen that its application 

 went beyond the instrument for which it was primarily designed. 

 The writer has used the camera lucida to a greater or less extent 

 in this manner for twenty-five years and has seen plenty of evi- 

 dence that others have used it in the same way. At one time it 

 was thought by certain manufacturers that the demand for an 

 instrument specially designed for this class of work would justify 

 the making and advertising of the instruments; but so far as I 

 am aware, all this apparatus has been now withdrawn from the 

 market. I do not know what the reason for this course may 

 have been. It would seem that the instrument met a scientific 

 need and that its sale should have been sufficient to keep it from 

 oblivion. The only conclusion one can arrive at is that for 

 some reason, the form of the instrument did not meet the need. 

 The following notes relate to a piece of apparatus which has been 

 S'radually developed during several years, and which has as its 

 object the application of the ordinary microscope camera lucida 

 to the purposes we have mentioned. 'It is a piece of apparatus 



