Scientific Intelligence — Arts. 397 



tints of the pearl to black wax, fusible metal, balsam of tolu, lead, 

 tin, and various other substances. The colours displayed by fusible 

 metal possess at first extraordinary beauty, which in a short time is 

 partially lost, owing to a change that occurs upon the surface of the 

 metal. 



A {qvi months ago, while engaged upon some experiments in 

 electrotyping, I was led to think, that, by this process, the hues of 

 the pearl might be readily transferred to those metals which, from 

 their hardness, are incapable of receiving impressions in mass, but 

 yet, on account of their freedom from oxidation, retain for a long 

 time a surface comparatively pure. I therefore took a Smee's bat- 

 tery, which I had just constructed, and after several experiments, 

 succeeded in obtaining small sheets of silver, radiant with the hues 

 of the shell. When seen by a single light, as that of a lamp, the 

 play of colours is surpassingly beautiful, scarcely inferior to that of the 

 pearl ; and where equal care was employed, the plate of silver, which 

 was formed eight months ago, rivals in brilliancy that which came 

 fresh from the battery a few hours since. 



The process by which this result is obtained is as follows : — The 

 first thing required is to prepare the shell. This is effected by 

 grinding and polishing it upon the back, in such a manner as to cut 

 through the numerous concentric strata that compose its substance. 

 When this is done, by the aid of a microscope the surface will be 

 seen covered with delicate grooves, some thousand in an inch, formed 

 by the sections of the concentric laminae, and this configuration gives 

 rise to the glowing tints of the shell. The next step is to obtain an 

 exact impression of this surface upon some good conductor of elec- 

 tricity. This we are enabled to do by means of fusible metal, if proper 

 precautions are employed in taking the impression. I pursue exactly 

 the same method as in taking the copy of a medal. After fusing the 

 metal, I pour it upon oiled paper, and when the air-bubbles cease to 

 rise through the metal, the oxide is skimmed from its surface with a 

 card, and as soon as it presents the appearance of a perfect mirror, the 

 shell is forced down upon it by a sudden pressure. When the metal 

 has cooled, I remove it from the shell ; and, having ascertained the 

 accuracy of the impression, immediately plunge it, before any change 

 of the surface can occur, into the silver solution, thereby completing 

 the circuit between the poles of the battery. In a few moments the 

 surface of the metal is frosted with silver, and the configuration of 

 the shell exactly copied. A sheet of silver, of sufficient thickness 

 to be easily removed with a penknife, will be deposited in the course 

 of five or six hours under favourable circumstances. The battery I 

 have employed consists of two plates of amalgamated zinc, and one 

 of platinized silver, six inches by eight. The working mixture is 

 sulphuric acid and water, the strength varying with the temperature, 

 and the amount of work to be performed. I have found a wine-glass 

 of acid to three quarts of well-water, at the temperature acquired by 



