532 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



cautiously heated to the fusion of the colophony, and graph- 

 ite dusted upon the plate and rubbed until the drawing ac- 

 quires a decided lustre. The plate is then placed in a half- 

 saturated solution of sulphate of copper until a black deposit 

 forms upon it, after which it is removed, wiped off, and re- 

 placed in the copper solution, the operation being repeated 

 two or three times, when the drawing appears in decided re- 

 lief. The free portions of the plate are then coated with a 

 mixture of gum arabic, ochre, white lead, etc., but not high- 

 er than the relief of the drawing, and when dry the whole 

 is rolled with transfer ink. The drawing may be further 

 strengthened by removing the layer of gum, immersing it in 

 water, and treating it again with sulphate of copper, until 

 the broad spaces are deep enough to allow it to be used in 

 the letter-press. 14 (7, CCXIL, 1874, 258. 



FIXING DESIGNS ON GLASS. 



According to a process patented by E. Dode, the surface 

 of the glass is first finely ground, and any design then paint- 

 ed on it with a mixture of anhydrous boracic acid, gum, and 

 water. When dry it is exposed to a temperature at which 

 the boracic acid fuses, and imparts to those portions of the 

 glass the usual lustre, and thus fixes the drawing. By mix- 

 ing various metallic oxides with the boracic acid, designs in 

 color may be produced. 15 (7, 1873, xxiv., 384. 



AUTOGRAPHIC REPRODUCTION OF DRAWINGS OF MACHINERY, 



ETC. 



The process almost exclusively employed for the multi- 

 plication of manuscripts is suggested by Tailly for the re- 

 production of drawings of machinery, etc. A tracing of the 

 drawing is first made in lithographic ink by placing it upon 

 several thicknesses of heavy, very smooth paper on a draw- 

 ing-board, and covering it with a piece of ordinary tracing- 

 paper, previously coated with an emulsion of tapioca in pure 

 water, and carefully dried, free from dust, and pasted by its 

 projecting edges to the drawing-board, with the coated sur- 

 face uppermost. When perfectly dry, the surface is render- 

 ed uniform by rubbing with erasing gum before the tracing 

 is made. The lithographic ink, obtainable in solid form, is 

 carefully dissolved by moistening it when pulverized with 



