'24 ANNUAL OF SCIENTIFIC DISCOVERY. 



ordinary furnaces, when it is termed cast steel. Steel maybe welded 

 to steel, or to wrought iron, under suitable conditions as to quality of 

 metal and temperature. The fracture of steel is peculiar, and varies 

 with the proportion of carbon and the treatment which the metal 

 may have previously received. It is more or less finely granular, and 

 when produced in the brittle state of the metal may be conchoidal or 

 shell-like, such as is presented by the broken surface of a lump of 

 glass. 



The processes now in operation for producing steel are founded on 

 two opposite principles, namely, putting carbon into wrought iron, 

 and taking carbon out of pig iron, which last, it will be borne in 

 mind, contains more carbon than steel. 



Carbon is put into iron in the following ways : 1 . By melting 

 wrought iron with carbon. This is the ancient Hindoo method of 

 preparing the famous " wootz." The principle has recently been 

 revived in making the so-called homogeneous steel or metal. Numer- 



^3 Cj 



ous specimens of wootz, sent from India, were exhibited in the Exhi- 

 bition, in the form of little conical ingots ; but there was nothing 

 peculiar about them to demand special notice. Not so with regard to 

 the so-called homogeneous metal, which has excited much attention 

 of late. It is extremely malleable and tough, and may be placed 

 midway between wrought iron and ordinary steel ; it may be regarded 

 as steel containing a low percentage of carbon. This is the metal of 

 which the celebrated English engineer, Whitworth, has constructed 

 his largest rifled ordnance. It is no doubt extremely valuable for 

 many purposes, but it is, thus far, difficult to produce it uniform in 

 quality. Examples of tubing made of this metal were shown, flat- 

 tened down vertically, and at first glance might be mistaken for India- 

 rubber. The metal, in this instance, we were informed, was produced 

 by melting pieces of Swedish iron and carbonaceous matter. In the 

 specification of a recent English patent granted for manufacturing 

 homogeneous metal, it is stated that scale, which falls off from steel 

 or iron during the process of hammering or rolling, is employed in 

 addition to the ingredients in common use for cast steel. 



2. Another process of introducing carbon into iron is known as 

 " cementation," and consists essentially in exposing flat bars of iron 

 imbedded in charcoal to about the temperature of melted copper dur- 

 ing many days. Carbon thus travels into the very centre of the 

 bars ; but how this takes place has not yet been clearly explained. 

 This process of preparing steel is an English one ; the furnaces are 

 termed " converting furnaces," and the bars of steel produced are 

 called " blister-steel," from their being studded here and there with 

 blister-like protuberances. 



A great number of examples of steel produced by the cementation 

 process were shown in almost every department of the Exhibition ; 

 but there was nothing about them which requires from us any partic- 

 ular comment. Until recently, all the steel at Sheffield, England, 

 was made by this process, and Swedish iron has been largely con- 

 sumed for the purpose. Different varieties of iron are known to 

 yield different qualities of steel, but the knowledge respecting these 

 differences is generally regarded as a trade secret. The prices of 

 Swedish iron in the English market vary considerably, i. e., from $160 



