Kew Mode of Printing Designs, ^c. 191 



rate of five miles per hour. The saving of the expense of 

 horses and track- roads promises to make this application of 

 human power very valuable. 



15. JVero mode of Printing Designs. — A discovery baa 

 b' en made in the department of Calvados in France, by 

 which the finest strokes of the crayon or pencil, upon por- 

 celain, may be infinitely multiplied. These strokes', traced 

 with a particular metallic composition upon the polished 

 surface of porcelain, are incrusted by the second applica- 

 tion of fire, without the slightest injury. The parts thus de- 

 lineated acquire a sort of roughness, insensible to the touchy 

 and only to be discovered by its perfect retention of ink, 

 which is easily wiped off the other parts of the surface. 

 This method seems to have decided advantages over litho- 

 graphy. 



16. Artificial Slates. — Artificial slates have been used id 

 Russia, which are said to be very valuable, as being lighter 

 than common slates, impermeable to water, incombustible, 

 and made of any required form or size. They have been 

 analyzed by M. George, who finds them to consist of bolar 

 earth, chalk or carbonate of lime, strong glue, paper pulp, 

 and linseed oil. The earthy materials are to be pounded 

 and sifted ; the glue dissolved in water; the paper is the 

 common paper pulp, which, after, being steeped in water, 

 has been pressed ; or it may be book binders or stationers' 

 shavings, boiled in water and pressed. The linseed oil is to 

 be raw. The paper pulp is to be mixed in a mortar with 

 the dissolved glue ; the earthy materials are then added, and 

 beaten up, and the oil mixed during the beating, as fast 

 as it is absorbed. The mixture is then spread with a 

 trowel on a plank, on which a sheet of paper has been laid, 

 and surrounded by a ledge to determine the thickness of the 

 layer, and is then turned out on a plank strewed with sand 

 to dry. When dry, they are passed through a rolling mil], 

 then pressed, and finally finished by a coat of drying oil. 

 The following are some of the various proportions recom- 

 mended. 



2 parts paper pulp, 1 glue, 1 chalk, 2 bole earth, 1 lin- 

 seed oil ; this forms a thin, hard, and very smooth sheet. 



