FIFTY YEARS OF MECHANICAL ENGINEERING. 537 



ton ; to-day they are worth thirty-eight dollars. It is confidently pre- 

 dicted by those who have made it a study, that the downward tend- 

 ency can not be checked, and that one cent a pound will be reached as 

 soon as the experimenters have worked out plans now in hand. 



Considering the many improvements which are now proposed and 

 tested, M'C can safely assume that the steel-plant of the future will 

 differ widely from the plant of to-day. All the available heat and all 

 the useful elements in the ore will be used. Briefly this is as follows : 

 The ores, limestone, and fuel will be placed in the furnace, the molten 

 metal will be run to converters, and there the foreign elements will be 

 removed by a blast, the metal then recarbonized and cast into ingots, 

 the ingots will be rolled into blooms, then the bloom into rails, and 

 the rails will then be placed on small cars, and, while at a temperature 

 of about 1,000° Fahr., will be placed in the flues of steam-boilers until 

 they have given up about 700° Fahr., and then passed on as finished. 

 The slag flowing from the blast-furnace will be placed on cars, and, 

 while at a temperature of 3,000° Fahr., be run into the flues of other 

 boilers used to generate steam for operating the blowers, rolls, etc. 

 This, in brief, is one of the proposed steps in steel-making, viz., the 

 utilization of all the heat in the coal, and afterward all the heat given 

 to the iron and slag by the coal ; by so placing the iron and slag as 

 to give up their heat again to boilers used to generate steam for the 

 roller-mills and blowing-engines, which in turn aid the smelting of the 

 iron. 



A rail-mill of 500 tons a day, at a low estimate, would secure heat 

 to run a 1,000 horse-power battery of boilers from the cooling rails 

 alone, and 4,000 horse-power in heat from the slag. Hence the steel- 

 plant of the future will have no heating-furnaces, no gas-producers, no 

 coal-consuming boilers, no cupolas, no ash-piles, and no fuel to be con- 

 sumed except that required to melt the iron. The converter-slag can 

 now be used instead of limestone by the new process. This, in brief, 

 will be, it is confidently predicted, the new rail-mill of the immediate 

 future. Everything is done by the aid of air, steam, and water. Mus- 

 cle will be in little demand, brains at a premium. In 1832 cast-iron 

 bridges existed of short span, but wrought-iron had not been used. 

 To-day we think little of trusses of 500 feet span, and suspension- 

 bridges of 1,000 feet ; while it is proposed to build a steel truss-bridge 

 over a mile long, with two spans of 1,700 feet each. In the power- 

 printing press, an invention of the eighteenth century, we find that 

 the last half-century has wrought wonders. In 1832 the best presses 

 could turn out about 1,000 poorly printed sheets of printed matter ; 

 to-day, thanks to Hoe's revolving type and the processes of electro- 

 plating and stereotyping, we have presses capable of printing 50,000 

 impressions an hour ; and, what is almost as wonderful, it will num- 

 ber, fold, and stick together the whole. Such a machine costs about 

 $100,000. 



