324 METALLURGY OF CAST IRON.
ment that makes the cupola irregular in its meltings so that it produces hot iron one day and dullish iron the next, also harder iron than desired with resulting bad work or heavy losses in castings. Knowing how very important it is to possess definite knowledge concerning what causes grades of iron to differ in their fusibility, I decided to experiment and learn, if possible, the effect of different combinations of the metalloids on the fusing point of iron. In searching for appliances that would give reliable data I failed to find anything satisfactory, and therefore set to work to devise something that would meet the requirements and at the same time withstand criticism. One objection I have to past methods of testing the fusibility of metals, is the failure to provide conditions similar to those used in actual founding. To meet the conditions of actual practice, I studied out a design of cupola (see Fig. 56, page 241) which is an original arrangement, so far as I know. The method adopted gives only comparative results and does not show the degree' of heat required to fuse any of the metals. Observations may be made and conclusions drawn from them as to the difference in the , time of melting which any grade of metal requires over another, when the two kinds of iron are charged in the respective sides shown. It will appear Lipon examination that like conditions must prevail in both apartments, and that if one grade starts or comes down quicker than another we know it to have a lower fusing point. By a series of such tests wre are in position to formulate a scale showing the combinations of metalloids requiring the highest heat, with the relative gradations 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/..