"BANKING" FURNACES AND CUPOLAS. 127
as this would better assist closing off all draft than were the last charge all iron, as a fine dust fuel, ore, etc., could be used on the surface to close up all cavities without calling for enough to cause injury, as would be the case with fine stock used to close up the cavities between pieces of iron, instead of fuel.
The principle involved in '' banking '' a furnace is one that has to a slight degree been practiced by some founders, as is seen in "American Foundry Practice," page 301. The author is so sanguine that the principles involved in banking are practical for application in cupola work, that he lately remodeled one of his cupolas with a view of experimenting to find out how many heats he could run without drop- . ping the bottom. At this writing conditions in our shop work have not permitted giving it a trial, the reason for which lies in the fact that the cupola which was prepared for this experiment was not large enough to run the heats demanded. The plans followed in remodeling this cupola consist simply in making all tuyere connections air-tight, raising the spout so as to permit of from .two to four inches of a heavier sand bottom, also in providing a double slide arrangement facing the tuyere openings which, when both were closed, left a space between them to be filled with loose sand that could be readily removed by a little slide pocket in the bottom of the sand space. These. two factors, combined with an arrangement to positively shut off the admission of any air where the main blast-pipe is connected with the wind-box, completed the arrangements. With this device it is the intention, after the first heat has been run off, if not a large one, to thoroughly melt down any iron thatd three months of the Warwick Iron Co. of Pottstown, Pa. is often surprising how rapidly, as about 75 per cent of the heat generated from the solid fuel is utilized. This is attained where one ton of coke will produce one ton of iron; and Sir........................ 2,720 "