THE CONQUEST OF NATURE 



wide. The bottom of these molds was flat but as the 

 metal cooled in them the upper surface became round 

 in shape, assuming a fanciful resemblance to a pig's 

 back. In this molding a great amount of time was 

 wasted in the slow process of cooling, and a large ex- 

 penditure of energy wasted in this handling and re- 

 handling of the metal. 



In modern smelting works, however, pigs are no 

 longer cast in sand molds, the molten metal from the 

 furnace being discharged directly into iron molds 

 attached to an endless chain. These molds are long, 

 narrow, and shallow, having the general shape of 

 sand molds. Each mold as it passes beneath the open- 

 ing in the furnace remains just long enough to receive 

 the requisite amount of metal to fill it, and then moves 

 on to a point where it is either sprayed with water, 

 or cooled by actually passing through a tank of water, 

 emerging from this bath with the metal sufficiently 

 solidified so that it may be dropped into a waiting car 

 at the turning point of the endless chain. In this 

 manner the charge from the blast-furnace may be 

 drawn, cooled, and converted into pigs, loaded into 

 cars, and hauled away without extra handlings or 

 loss of time, the whole process occupying practically 

 no more time than the initial step of tapping by the 

 older method. 



Where the contents of the blast-furnace are to be 

 converted into steel at once, the molten metal is run 

 off into movable tanks which carry it directly to the 

 steel furnaces. These tanks, holding perhaps twenty 

 tons of metal, are made of thick iron lined with fire 



[288] 



