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Io8                      METALLURGY   OF   CAST   IRON.
shown standing ready to drive the cutter into the runner to stop the metal from flowing to the first bed. The second man seen on the left stands ready to ravel out the branch runner to the pig bed. The third man having a pole in his hand is supposed to be breaking up the crust of slush formed in the front of the metal as it first comes down the main runner. These last three men are simply placed in position shown to illustrate their work, as if metal had been actually running down the runner as above described. To those never having seen a casting house, Fig. 34 should give a general idea of the methods employed for moulding and casting pig metal.
Moulders are often employed at a furnace to make moulds, open and closed, to be poured with metal as it comes down the runner. How to regulate the flow so as to stop it as soon as the mould is filled is a trick often worth knowing for application even in a foundry. At Fig. 26 is seen a section, through A B of Fig. 27. The moulds shown are supposed to be ." open sand'' plates, which should be as uniform in thickness as possible. By the plan shown, if the metal is as ' hot "as is generally obtained, the plates can be made not to vary over y$ inch in thickness, which is as close as a founder can generally run them where he has inetal in a ladle supposed to be under perfect control. To explain this principle, attention is first called to Fig. 25, which is a section of the main runner. At the dotted lines N and M is seen the depth to which the branch runners connecting the sow j i. 1 main runner are generally made and which are sv.;> posed to drain all the metal from the main runner u, ...  " cut off " by the " cutters " B, as seen in Figs. 24 ji thean opening to admitt it struckat the regular notch.    It 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     "