154
THE POPULAR SCIENCE MONTHLY.
"Formerly furnaces were constructed much simpler, and no specific or exact proportions were observed; and it was not considered necessary that the walls should have any fixed dimensions, either as to thickness or height; but (according to Agricola, who was the first to describe them) the whole structure was rude,
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/PSM_V38_D166_A_reverberatory_furnace_of_1647.jpg/500px-PSM_V38_D166_A_reverberatory_furnace_of_1647.jpg)
Fig. 4.—A Reverbatory furnace, (1647.)
loose, and imperfect, their daily product of iron was small, and they consumed a very large quantity of charcoal; but afterward, when it became evident that regularity in smelting insured excellence of product, and at the same time the realization of