142 ANNUAL OF SCIENTIFIC DISCOVERY. 



On the figure photographed, or traced by pencil, the artist 

 proceeds to make his drawing with little tools like needle-points, 

 fixed in wooden handles. These tools should vary in size, or 

 rather in the thickness of the point, according to the nature of the 

 ■work intended to be accomplished. It will be found most advan- 

 tageous to use tools one side of which has been filed flat, and a 

 curve given to them near the point by bending them while heated 

 in the flame of the gas. Every touch or stroke of the artist should 

 penetrate through the waxy varnish to the surface of the plate, 

 which, being black, reveals every touch ; the work thus appearing 

 black on a white ground, in the same manner as if it were eft'ected 

 by pen and ink on white paper. 



The coarseness or heaviness of the lines depends upon the tool 

 by which they are cut ; hence broad lines require a tool flattened 

 at the point like a chisel. The drawing must be made as in 

 nature, or non-reversed. 



When the picture is examined and found to be right, it is dusted 

 over with plumbago, which, by means of a bushy camePs-hair 

 pencil, is distributed through every line and over every part of 

 the surface. Although we find that other conducting substances, 

 such as bronze powders, act better than plumbago, we have very 

 beautiful pictures in which the coating is the same as that here 

 described. 



The plate thus prepared is immersed in an electrotype cell, and 

 a thin tissue of copper is deposited on it by the battery. When 

 the i^late has been immersed at night, we find in the morning that 

 the deposit of copper is sufficiently thick to allow of its being 

 removed. The battery we use is Smee's, and the depositing solu- 

 tion is the sulphate of copper, rendered decidedly acid with sul- 

 phuric acid. 



The cast thus obtained must be backed up with soft metal, and 

 in this state it will, if printed from as a wood engraving, yield an 

 exact fac-simile of the original drawing. 



If it be required to lower broad masses of white, this can be 

 effected in one or other of the following ways : — 



After the drawing has been finished, and before it is brushed 

 with black lead, paint over the broad masses of white with melted 

 wax, and let the thickness of the mass thus painted on the surface 

 be determined by the area of the white portion, care being taken 

 not to approach too closely to the lines of the drawing. This 

 having been done, proceed with the plumbago as already directed. 



Another way by which to lower the broad whites is to take a 

 cast in plaster of Paris from the original plate, and in this cast to 

 lower any part required by means of a suitable gouge-shaped 

 tool. From the plaster block thus trimmed may be obtained, by 

 means of recasting in plaster and stereotyping, any number of 

 metal blocks in a condition ready for printing. 



We have in our possession some pictures which have been ob- 

 tained from surface blocks prepared nearly as described, and 

 which are so fine and delicate as to warrant any person, unac- 

 quainted with the method of their production, in believing that 



