964 Tkansactions of the Amebic ax Institute. 



adapted for magnets. He inquired the reason of tins, and was told 

 that the iron was from the Leliigh mines, and was always of the same 

 quality. The old method of case-hardening iron by packing the iron 

 in a box with animal refuse, such as scraps of horns, hoofs, leather 

 and the like is by some preferred. These materials are charred just 

 •enough to permit their pulverization. Bone dust ma}^ be substituted 

 in place of these. The articles are packed with the material in an 

 iron box, carefully luted with clay, and placed in the furnace, where 

 it is allowed to remain for a length of time proportioned to the 

 thickness of the film of steel to be formed upon the iron. An hour 

 after the box is thoroughly heated through, ma}' give a thickness of 

 one-sixteenth of an inch, and a longer time in proportion. The box 

 when taken from the iire is emptied into pure cold water, and the 

 articles may be dried by shaking them in saw dust. Case-hardening 

 by coating the surface of the iron with a paste of the prussiate of 

 potash, and heating in a clear fire, is more convenient than the 

 former, but the results are not considered so good. 



Dr. L. Bradley remarked that it was well known that water cooled 

 steel much quicker than oil, as articles hardened in oil did not require 

 any tempering. 



Mr. Chas. E. Emery stated that a patent has recently been taken 

 out in tliis country for a com])ound of sulphuric acid, and other sub- 

 stances, which are mixed with the water to make a bath for tempering 

 steel. The articles to be tempered, after being highly heated, are 

 dropped into the solution, which cools them with sufficient rapidity 

 to get the proper temper. By this process steel springs for railroads 

 are reduced in weight fully twenty per cent. This promises to be 

 a most important invention. The springs require a less number of 

 leaves on account of the slight damage done to the steel. The bath 

 cools the metal with just sufficient rapidity to get the proper temper. 

 There are two ways of atmealing steel ; one is to allow it to cool 

 elowly in the ashes of the fire, and the other is to heat the steel to a 

 cherry-red and allow it to cool until the color can just be distinguished 

 in the dark, then to be plunged in water, and will l)e found to be 

 very soft and can be cut with the greatest ease. 



Mr. Beckers said that the hardening of steel and tlie case-harden- 

 ing of iron, although sometimes attained by similar means, are wholly 

 different in character. In using the prussiate of jjotash but a small 

 thickness of the iron is coated with steel, and if the iron is exposed 

 for a length of time the steel will penetrate so that in time the iron 

 can be transformed to steel by simply continuing the process. 



