30 



Dr. Schunck on tlic Formation of Indigo-hlue. 



at a convenient lu-ii^ht in a wooden box, of which abed, fij;'. 1, 

 rt'in-esents the front. This box is cUised at the two sides, but 

 open at the front and back from the shelf upwards. It must be 

 sufficiently wide to allow the dish to slide easily in and out, but 

 from front to back it must be so deep as to leave a space of about 

 half an inch between the front and the dish. At the distance of 

 about ] I inch from the back of the box, there is fixed in a per- 

 pendicular position a board /", the upper and side edges of which 

 are firmly attached to the toj) and sides of the box. The lower 

 edge of this board is about on a level with the uj)pcredge of the 

 tin dish, and is accurately fitted to a shelf, g, which is suspended 

 by means of two u])right pieces of wood, hJi, 2\ inches deep, 

 resting on two ledges, i i, fixed to the sides of the box. The 

 spaces between h h and the side walls of the box must be suffi- 

 ciently wide to allow the sides of the tin dish to move easily uj) 

 and down in thein. By means of supports, n n, inserted between 

 the tin dish e and the shelf o, the former may be raised so as to 

 bring the surface of the liquid contained in it close to the shelf ^, 

 which is thus made to hang down within the dish. When the 

 apparatus is to be used, the spaces pp ^^^^ between the edges of 

 the dish and the ledges ii, are closed as tightly as possible by 

 means of flat plugs of wood, so as to cause the current of air 

 passing through the apparatus to sweep over the whole surface 



Fig. 1. 



'™™T!i!l!Il!SlM 





Fis- 2. 



jILJ 



_^^j 



of the liquid, and the front of the box is closed by means of a 

 U-;\mr, J khn, covered with muslin aiul sliding up and down in 



