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COMPARATIVE FUSIBILITY OF FOUNDRY METALS. 327
bed of the fuel the same height on both sides, also to have each grade of metal as nearly uniform in size as possible, and evenly charged. After this, coke is filled in until the cupola is stocked to its brim, when it is ready for the blast.
The first test heat made, as seen by the Table 70, consisted of 150 pounds on each side, it being put in with 50 pounds in two charges after the bed of 50 pounds was on. This plan was found to be objectionable for comparative testing, as it showed wherein errors might easily be made by reason of uneven charging, the escaping flame making it too hot for the charger to always place the iron in evenly. After this first heat no more metal was charged than the bed could carry well, thus permitting all iron to be carefully charged before the blast went on. The plan adopted for comparative tests of Table 70 was to make at least two casts of each grade, the first being that of the metal in its original state, each grade being broken to uniform size, as far as possible. This, in being melted down, was run into moulds that gave blocks weighing about 15 pounds each and in size 2 ^ x 4 x 6 inches. For the second cast of each grade these blocks, in the larger heats, were broken in two pieces, but where there were only two blocks for each side they were charged whole. The idea of running the first heat of pig metal or scrap into blocks, as stated, was to obtain metal that would be closely uniform in size and weight and better insure like conditions in making a comparative test, an. important requisite. This appears in Table 70, in the columns marked alternately "pig" and "block." Up to the time of writing this paper I have made nineteen comparative; In. charging any metal for a comparative test, care must be exercised to have theations of others, down to that most readily fused.the bottoms. Our «Mj)pnrheii.sion as to loss of iron through slai;" was r> ">'•• I I O/..