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UTILITY   OK   CHILI,   TKSTS.                         433
quickly from a chill at one time than another, will give a different thickness of chill.
Third. The least difference in the grade of an iron causes a variation in its contraction, thereby causing one quality of iron to pull away from a side chill more than another.
Fourth. The thickness of chill used affects the depth of the chilling in the casting, up to the limit of the chill being affected, in suddenly extracting heat to counteract the carbon at the surface body of a casting being evolved into any graphitic carbon.
Fifth. The thickness of a casting affects the depth of a chill.
Sixth. Degrees of fluidity affect the chill. A hot-poured iron will chill deeper than a dull one. Sec page
It is shown by the above that certain conditions have an effect in regulating the depth of a chill in castings, and that it is impossible for any one to tell what the1 exact lt chill " will be in a, casting by means of a chill test; but. where one has had considerable experience with llu. special easting and takes into consideration all tin* elements in the case, he can elosely draw his own deductions as to what depth of chill he may expect in the eastings. To do this we must especially consider the thickness of our easting in connection with the iron used, also whether the easting will remain in eon-tact with its chill mould, or pull away from it; also the fluidity of the metal with which a casting is poured. Further information on chilling is found on pages jj5, 502 and 513.act that east iron will stretch that saves many from having their ignorance on this subject exposed. There are many castings made that would not hold to-er form, which I will call heat resistance, and which displays its power to stretch iron by reasonnts,    bin    of   aamples of which in every-day practice the writer will cite further on.cibly illustrates the great reason why the founder has to fear sulphur in fuel, high-sulphur iron, and to            j