paper is decidedly the best we have met with. Every sheet should 

 be examined by a strong light, and all those rejected which have 

 any spot upon them, as also those which are found on trial to imbibe 

 the solutions unequally. One side of the sheet should have a pencil 

 mark upon it, by which it may be recognised. The blotting-paper 

 must be the white wove, and the sheets used in different stages of 

 the process should be kept separate. A trough of Berlin Ware, 

 which is not acted upon by chemical preparations, and a slab of 

 the same material are also required for preparing and washing 

 paper. 



COPYING FRAME. 



All that is absolutely essential for this purpose, is a piece of plate 

 glass of a sufficient size, and a board of similar dimensions covered 

 with soft flannel : these, with the prepared paper and object to be 

 copied placed between them, may be kept in contact by three or 

 four binding screws. But the most convenient apparatus is re- 

 presented at Fig. 1, consisting of a frame in which a piece of plate 



Fig. i. 



glass (a) is fixed, with a wooden back covered with a cushion of 

 flannel. The back may be removed to admit of the introduction of 



