202 GENERAL SCIENCE 



ing to the uses to be made of the steel, and the qualities 

 desired in it. Various small proportions of nickel or of other 

 metals are sometimes combined in steel to give it desired 

 properties fitting it for certain uses in parts of machinery 

 where great powers of endurance are required, or in the 

 armor of battle ships where impenetrability without brittle- 

 ness is necessary. 



The separation from the iron of the earthy material of the 

 ore along with the ash and clinkers from the fuel is facili- 

 tated by the use of limestone as a "flux. " In combination 

 with sand present in the ore the calcium carbonate at the 

 high temperature of the furnace forms a molten glass-like 

 mass which floats as a viscid liquid above the molten iron, 

 and when withdrawn as "slag" from the furnace from time 

 to time it carries with it the refuse material of the furnace. 

 The alternate layers of fuel, flux, and ore are fed at frequent 

 intervals in at the top of the furnace stack where they are 

 hoisted by machinery continuously in operation so long as 

 the furnace is "in blast." 



The material mixed in the furnace with the fuel and ore as 

 a flux varies in chemical nature and in amount according to 

 the earthy constituents of the ore. Indeed, throughout 

 the whole series of operations from the raw ores to the finished 

 metal product exact chemical knowledge of the material 

 used and of the changes occurring in it must be maintained. 

 This makes possible an output of metal of any desired quality. 

 No "guessing" at results is permissible in the industries. 

 The exactness attained in quality of manufactured products 

 by reason of applied chemical knowledge is strikingly seen 

 in the fact that steel of any certain quality is sold under 

 contract for delivery a year or more later, and before the 

 ores or the coal for reducing them have been mined. The 

 makers of various fabrics contract for the delivery of goods 

 of certain desired colors before the chemicals to be used as dyes 



