158 



Electrography. 



3. A connection must also be established between the two fluids 

 by means of a metallic strap or wire ; to the end of this strap 

 which is in the metallic salt, must be soldered the object to be 

 copied, which must also be a metal or at least have a metallic sur- 

 face ; to the other end of this metallic connection, which is in the 

 acidulated water, a piece of zinc must be attached by soldering. 



The accompanying figure taken from Mr. 

 Spencer's pamphlet, will render the forego- 

 ing conditions of the experiment quite plain. 

 A, is a glass vessel, (a common drinking tum- 

 bler answers very well;) B, is a straight tube 

 of glass, in this case an argand lamp chim- 

 ney, having the lower end closed by a dia- 

 phragm of plaster, brown paper, or animal 

 membrane ; C, the object to be copied ; E, 

 a piece of zinc ; F, the copper connecting 

 wire soldered to C and E ; D, a cover of any 

 convenient material, (a cork or piece of wood,) 

 fitting A, and provided with two holes, one in the center for hold- 

 ing the glass B in its place and another to permit the wire F to 

 pass. The apparatus being thus arranged, pour into A, a satura- 

 ted solution of sulphate of copper warmed to 100° or 120° P., 

 and into B, a warm weak acid water to the same level as the so- 

 lution in the outer vessel.* 



A more simple form of apparatus, 

 and one which we have used with good 

 success, is shown in the following fig- 

 ure ; we describe it because we believe 

 it is much better adapted to the means 

 of the inexperienced experimenter than 

 the foregoing, and its manipulation is 

 also much simpler. 



A, is an earthen ware pot of any requi- 

 site capacity ; B, 6, the porous division, 

 which may be made by casting plaster 

 of Paris across from side to side, and 



* Mr. Spencer objects to the use of an apparatus where the plates are verticaJ, 

 because the deposition is of unequal thickness ; but we have found no difficulty 

 if the solution is kept saturated. 



