METALLURGY OF CAST IRON. At M, Fig. 84, is seen an iron pattern from which sand or chill moulds may be made. At A, Fig-. 85, is an iron box three inches square by eleven inches long1, in FIG. 85. which the pattern M has been moulded to make a dry sand mould and is filled with molten metal. The cut shows a moulder in the act of pouring the contents -he gases could rise upward to find relief through the cope or top part of the mould, and which, if not well vented, or of a porous and fairly dry character, will then often hold the gases from going further and form cavities in the cope side of castings, such as seen at T in sample No. 23 of the same figure.