163 MR. J. C. DYER ON THE ORIGIN OF 



The medal (an eagle, motto, &c.) being engraved or 

 sunk on a die of softened steel, the die was then hardened 

 and served to stamp or impress the design, in relief, upon 

 another softened steel die, which latter being hardened, 

 was employed as a stamp to transfer or raise the figures 

 on the silver, rolled very thin, to form the medals. 



By this process Mr. Perkins was enabled to supply a 

 vast number of the medals, from which he derived a con- 

 siderable profit, as also great credit for his success, and 

 encouragement to extend his new transferring process to 

 other branches of engraving. 



His next application of the principle was to the printing 

 of bank-notes, with very elaborate engravings, to discourage 

 or prevent forgeries, by reason of the cost and difficulty of 

 imitating them by the hand-engraving of the forgers. For 

 this purpose Mr. Perkins procured some cast-steel plates 

 (about half an inch in thickness), and after making their 

 surface smooth and level, he subjected them to the decar- 

 bonizing process (explained in his patent), by which the 

 surfaces, to the depth of about y^ of an inch, were con- 

 verted into very soft and pure iron. On these were then 

 engraved, by hand, the letters and. designs for the bank- 

 notes, and the entire surface of the plate was covered with 

 minute letters or figures, to render the bare labour of coun- 

 terfeiting them a great hindrance, as well as that of the 

 difficulty of imitation. The steel plates so prepared and 

 engraved were next recarbonated by his process of cementa- 

 tion with animal carbon, and then they were hardened and 

 tempered for use. 



But instead of printing the notes from these plates, they 

 were used as dies for making others to print with. Thus 

 he prepared a cast-steel cylinder (its circumference equal to 

 the length of the plate), which in like manner was decar- 

 bonated at the surface, and then mounted in an apparatus 

 adapted for turning it over the engraved plate, under a very 



