the center of the furnace. The chimney (shown at the right of the cut, broken in three places for convenience of illustration) is usually from thirty to forty feet in height, provided with a damper operated by a lever at its top, and its flue is usually eighteen inches square. Fig. 25 is a section of the furnace (on line G, H, Fig. 24), showing the form of its interior in plan, and the relative position of "fire-grate," "working-chamber," and "chimney-stack." In mills driven by steam power it is not now uncommon to place a horizontal cylindrical flue-boiler over each puddling and heating furnace, and generate the steam required to run the mill by passing the heat, that would otherwise go to waste up the chimney, underneath the boiler, and thence through the flues to the chimney-stack. This construction was the invention of the late John Griffen, who at the time of his death (January 14, 1884) was General Superintendent of the Phoenix Iron Company at Phœnixville, Pa. The idea of utilizing the waste heat of puddling and heating
furnaces for the making of steam was, however, quite old at the time he brought out his arrangement.
When, in 1846, Mr. Griffen erected at Norristown, Pa., for Messrs. Moore & Hooven, the first mill in which all the steam was generated in boilers placed over the furnaces, the wise fools were in strong force; and Swank tells us that "Mr. Griffen met with much opposition from observers while employed in constructing the mill upon this plan, and many predictions were made that the new arrangement would prove a failure. It was a great