1METALLURGY OF CAST IRON.
Forty*eight-hour and 72-hour coke refers to the time the coal is subjected to the coking process in the oven. Table i, page 13, shows that 48-hour and 72-hour coke varies in the length of time it is in.an oven, and that the actual time coal is coked is largely regulated by local conditions best suiting the working convenience of the coke workers in going the rounds of their ovens; and we might say we have instead of 48-hour and 7 2-hour coke, two- and three-day coke. Where machinery is used instead of mules and hand labor in charging ovens, the coal is insured a longer coking than forty-eight and seventy-two hours, as by the means of machinery the ovens can be charged earlier in the day and the coking resumed. Seventy-two hour coke, which is used chiefly by foundrymen, is generally due to coke remaining in the ovens over Sunday, which day the cokers do not work. Seventy-two hour coke is not always up to the high standard that many claim for it. The author has melted with furnace, or 48-hour coke, for six months at a time, and he cannot say that the fact of its being 48-hour coke caused it to be unsatisfactory, when the difference in price was considered. Nevertheless, as a rule, 48-hour coke is of less value as a melter than 7 2-hour coke, as the latter is generally a harder, larger, and cleaner fuel. As large a coke may be produced from a 48-hour as a 7 2-hour burning, but owing to the conditions which permit furnacemen to use smaller and more dusty coke with less evil results than are apt to follow its use in cupola work, 48-hour coke-is not selected nor handled with the same care as 7 2-hour coke, and hence the former will give a greater yield from the same amount of coal. The method usedt has proved an excellent fuel for this and kindred uses.''