HISTORY OF ELECTRO-METALLURGY. 7 



of a wire and solder, with a zinc plate which dips into the latter. A 

 slow electric action is thus established through the pores of the plas- 

 ter, which it is not necessary to mention here the result of which is 

 the precipitation of minutely crystallized copper on the plate of that 

 metal, in a state of greater or less malleability according to the slow- 

 ness or rapidity with which it is deposited. In some experiments of 

 this nature, on removing the copper thus formed, I remarked that 

 the surface in contact with the plate equalled the latter in smooth- 

 ness and polish, and mentioned this fact to some individuals of my 

 acquaintance. It occurred to me, therefore, that if the surface of 

 the plate was engraved, an impression might be obtained. This was 

 found to be the case ; for, on detaching the precipitated metal, the 

 most delicate and superficial markings, from the fine particles of 

 powder used in polishing, to the deeper touches of a needle or a 

 graver, exhibited their correspondent impressions in relief, with 

 great fidelity. It is, therefore, evident that this principle will admit 

 of improvement, and that casts and moulds may be obtained from 

 any form of copper. 



" This rendered it probable that impressions may be obtained from 

 those other metals having an electro-negative relation to the zinc 

 plate of the battery. With this view, a common printing type was 

 substituted for the copperplate, and treated in the same manner. 

 This also was successful ; the reduced copper coated that portion of 

 the type immersed in the solution. This, when removed, was found 

 to be a perfect matrix, and might be employed for the purpose of 

 casting, where time is not an object. 



" It appears, therefore that this discovery may be turned to some 

 practical account. It may be taken advantage of in procuring casts 

 from various metals, as above alluded to ; for instance, a copper die 

 may be formed from a cast of a coin or medal, in silver, type metal, 

 or lead, &c., which may be employed in striking impressions in soft 

 metals. Casts may probably be obtained from a plaster surface sur- 

 rounding a plate of copper ; tubes or any small vessels may also be 

 made by precipitating the metal around a wire, or any kind of sur- 

 face, to form the interior, which may be removed mechanically, by 

 the aid of an acid solvent, or by heat. 



" C. J. JORDAN." 



" To the Editor of the London Mechanics^ Magazine " 



Clear and perspicuous as this letter is, it did not attract the slightest 

 notice. And a few weeks after, we find that its existence was for- 

 gotten even by the editor of the magazine in which it appeared. 



Spencer's First Printed Paper upon Electrotype. Mr. Spencer's 



communication, referred to above, was, in consequence of some mis- 

 understanding, not read at the meeting of the British Association, 



