5*6 METALLURGY OF CAST IRON. height metal will rise in a long, thin wedge. These fluidity and life measuring strips are ten inches long by three-fourths of an inch wide, as at S, in Pig. 121, page 509. The base of these strips measures one-eighth of an inch thick, and they run up to a knife edge at the top. They are a very sensitive thermometer to denote both the fluidity and life of metal, as will be found by any one adopting the system. Having the fluidity strips poured in a vertical position, as arranged in this system in connection with the heavier bodies, FIG. 124.ŚMOULD BOARD, BOTTOM PLATE AND COPE HALF OF FLASK. prohibits any forced or unnatural pressure to be exerted, so as to have the strips falsely record the fluidity of metal when bars are poured. The metal cannot rise in the fluidity strips any faster than in the test bar, and hence the strips must have a gradual rise. Their measurement can be accepted as practical and representing the true fluidity and life of metal at the time it is poured. Take such fluidity strips and cast them flat (See Fig. 71, page 375); the length they '' run '' are largely determined by the way they arerecording the full chilling qualities of the iron. At V V, Pig. 126, page 522, can be seen the chill used in this system. It is simply two half-circles three inches long by three-eighths of an inch thick, having a hole drilled in them to fit over the pattern tips W \V, Pig. 122, These chills are set on over the pattern before starting to fill the nowel with sand, and in shaking out, must, of course, be picked up and used as long as they last. They are made of a soft steel shaft, which, after being drilled or bored out, are then split as seen. See page 502.