Page:Popular Science Monthly Volume 38.djvu/469

Rh At first nothing but the coal was dumped into the furnace, the ore and limestone being charged with iron pans similar to the baskets formerly used at charcoal furnaces; the limestone was broken quite small.

After the success of this furnace was assured, furnaces in which mineral fuel (either anthracite or coke, or a mixture of the two, with an occasional use of raw bituminous coal) was exclusively used rapidly increased. Various changes and improvements naturally took place as time passed and experience was gained; but year by year the volume of iron smelted by mineral fuel increased relative to that made by charcoal, until in 1889 it reached the grand total of 7,871,779 tons, while "the make" of the charcoal furnaces amounted to but 644,300 tons.

Notwithstanding the practical demonstration by David Thomas that mineral coal could be successfully used for smelting iron, charcoal furnaces continued to be built. The general appearance of such furnaces as were erected during the fifteen years following the year 1840 is well represented in Fig. 32, of which Fig. 33 is a vertical section. As a rule they were no better in idea, and but little in execution, than those described by Swedenborg a century before; but, after the year 1855, the construction of furnaces began to receive more careful attention, and by the year 1860 the best-informed metallurgical engineers (whose profession was just beginning to be recognized) had discovered that uncouth bulk and crude workmanship were not desirable features in a furnace for the making of pig iron. Yet, nevertheless, some of the stragglers who are always found hovering in the rear of the grand army of progress, and who never know what is going on at the