160 Electrography. 



with a brush, the mould being previously warmed slightly, so that 

 the wax may be more evenly distributed. The wire connecting 

 the mould with the zinc, must be soldered to the back of the lead- 

 en impress. No sooner are the poles of this small battery con- 

 nected and placed in their respective solutions, than the deposit 

 of metallic copper commences on the mould, copying with in- 

 conceivable delicacy, all the most minute lines and even the 

 shades of polish which may be on the face of the matrix. Great 

 care is necessary to see that the surface to be deposited upon, is 

 clean and bright, for the least grease or foreign matter, even such 

 as would come from the fingers, will prove an impediment to the 

 uniformity and beauty of the result. From one day to three days 

 are necessary, to obtain a copy of a medal or of any object of similar 

 size, according to the required thickness of the deposit. During 

 this time, the apparatus should be placed in a situation where the 

 temperature can be maintained at about 100° or 120°, and the 

 saturation of the cupreous solution should be carefully insured, by 

 suspending in it a gauze bag containing crystals of the salt, which 

 will be dissolved as the strength of the solution declines. If this 

 latter precaution be neglected, the free acid resulting from the 

 constant decomposition of the sulphate of copper will interfere 

 materially with the success of the result, and the tenacity of the 

 deposited copper, as well as the rapidity with which the process 

 proceeds seems to depend in some measure, on the temperature 

 being moderately elevated. 



After the deposit has gained sufficient thickness, it may be ea- 

 sily removed by immersing the united metals in boiling water, or 

 better by holding the matrix for a moment over a spirit lamp, or 

 if large and heavy, over a chaffeur of burning coals, when the 

 different expansibility of the two metals will cause an instant sepa- 

 ration, with a smart crackling sound. The separation of the depos- 

 it, where it has fallen on a matrix of copper, is not however, so ea- 

 sy, but it may generally be effected without serious difficulty, if 

 previously to placing the matrix in the solution, its warmed surface 

 be slightly covered with fine bees' wax, which must then be re- 

 moved with great care from all parts of it, while still warm, rub- 

 bing it briskly with a clean fine cloth, all the wax seems to be re- 

 moved, but in fact, a film remains which is sufficient to prevent 

 chemical union between the surfaces, although if carefully done, 

 not interfering with the deposition of the metal. The casts thus 



