606 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



of two parts of finely powdered silver-litharge, and one part 

 of dry white lead, add as much of a mixture of three parts 

 of boiled linseed-oil and one of copal varnish as will form a 

 doughy mass. It is only necessary to cover the lower face 

 of the medal with this cement, press it upon the glass, and 

 remove the excess of cement. 13 (7, May 15, 1873, 655. 



A PERMANENT PASTE. 



The following process will, it is said, afford an unusually 

 adhesive paste, adapted to fastening leather, paper, etc., with- 

 out the defects of glue; and, if preserved from evaporation 

 in closed bottles, will keep for years. Cover four parts, by 

 weight, of glue, with fifteen parts of cold water, and allow it 

 to soak for several hours ; then warm moderately till the so- 

 lution is perfectly clear, and dilute it w^ith sixty-five parts of 

 boiling water, intimately stirred in. !N'ext prepare a solution 

 of thirty parts of starch in two hundred parts of cold water, 

 so as to form a thin, homogeneous liquid, free from lumps, 

 and pour the boiling glue solution into it with thorough stir- 

 ring, and at the same time keeping the mass boiling. 8 (7, 

 1873, Lx., 144. 



LIQUID PARCHMENT. 



According to Dr. Hoffmann, a fluid by this name, consist- 

 ing of gutta-percha softened and soaked in ether, is especially 

 adapted for forming a coating for pictures and cards, which 

 permits the removal of dirt Avith a moist I'ag. Pencil and 

 crayon drawings may be rendered ineffaceable by sprinkling 

 with this liquid by means of an atomizer, an exceedingly del- 

 icate film remaining on the evaporation of the ether. 14 C, 

 1873, CCVIII., 235. 



now TO YARNISH. 



It is essential to the brilliancy and adhesiveness of varnish 

 that the temperature of the atmosphere in which it is put on 

 should be as high as can conveniently be borne, since, at a 

 lower degree of heat, a deposit of the invisible moisture in" 

 the atmosphere takes place before the solvent in the varnish 

 has sufficiently evaj)orated. This may occur even on fine 

 summer days, giving a milky, turbid apj^earance to the var- 

 nish, which can only be avoided by bringing the temperature 



