/'///. .">. 



fig. I. 



/•>,,. 2. 



Figure io. — Asa Spencer's "engine lathe for engraving oval or geometrical 

 figures upon metal or other surfaces." "Fig. i ," elevation of swinging head- 

 stock, pivoted at c, c, with "oval chuck formed as usual" at right end; "Fig. 2," 

 end view, with oval chuck removed (the adjustable cam S and follower — 

 attached to arm t — are shown only in this view) ; "Fig. 3," rear end view. Tool 

 carriage is not shown. From London Journal of Arts and Sciences (1820), ser. 1, 

 vol. 1. 



The steel plates were annealed in contact with 

 oxide of iron in close retorts until soft enough to be 

 engraved with the ease of copper plates, then they 

 were recarbonized and hardened. I was too young 

 at the time to fully understand the philosophy of the 

 operation, but not too young to watch with great 

 interest Mr. Perkins' manipulation. The care he took 

 to have the water rapidly pass over his plates to carry 

 off the heat forcibly impressed me. 



He had small steel cylinders that he used in trans- 

 ferring the engravings. His mode of handling these 

 in hardening them was very interesting to me. He 

 heated them in what he called mufflers closely packed 

 in with carbon which was made of wood charcoal, 

 and about an equal portion of a coal made of leather 

 scraps that he burned in crucibles. I have a clear 

 recollection of what he called his muffler furnace and 

 also of the mufflers themselves as I have carried them 

 to him from Miller's pottery on Filbert Street to our 

 shop. They were tubes flattened on one side Q 

 made of fire brick clay and about V, inch thick. 

 They were long enough to reach from side to side of 

 his furnace over a charcoal fire made on a grate, 



charcoal being added from time to time so that the 

 fire surrounded the mufflers. 



It was a long heating process and to my boyish 

 question of why he did not heat them in the open 

 fire, his reply was that they would be ruined by scale 

 if the air was not entirely excluded, and to the 

 question as to why he was so long about it and so 

 careful in watching the fire, he said it was necessary 

 as a part of the hardening process. 



I do not think the wood and leather coal dust were 

 all he used in packing his cylinders in the mufflers, 

 but I collected the leather scraps for him and when 

 burned pounded them together with the wood coal 

 in a great iron mortar. When Perkins was satisfied 

 his cylinders were in condition for their cold bath, 

 if from any cause they refused to be pushed from the 

 muffler he never hesitated to break the muffle, seize 

 the cylinder with heated tongs and plunge it into a 

 gushing stream from a hydrant. 



The hardening of steel by a quick running stream 

 of water or by jets was a frequent subject of discussion 

 between Father, Perkins, and visitors to the shops, to 

 which I have listened with great interest and atten- 

 tion. Among the most frequent visitors that I 



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