. Transactions. iquid jiortionthan if all froze at the same temperature. In other words,the austenite is capable of making, and does make, a continu-ous structure with a freezing-point higher than the eutectic,whereas, the graphite in the hyper-eutectic irons cannot form EFFECT OF HKill CARBON ON CHARCOAL-IRON. 329 any continuous structure, and does not affect the freezing-tem-perature of the principal portion of the exterior mass. We have here also the obvious action that when there is car-bon in excess of the eutectic ratio, the excess falls out, and thewhole mass, except these isolated flak
. Transactions. iquid jiortionthan if all froze at the same temperature. In other words,the austenite is capable of making, and does make, a continu-ous structure with a freezing-point higher than the eutectic,whereas, the graphite in the hyper-eutectic irons cannot form EFFECT OF HKill CARBON ON CHARCOAL-IRON. 329 any continuous structure, and does not affect the freezing-tem-perature of the principal portion of the exterior mass. We have here also the obvious action that when there is car-bon in excess of the eutectic ratio, the excess falls out, and thewhole mass, except these isolated flakes of primary graphite, is€omposed of eutectic. In the hypo-eutectic irons, on the otherhand, it is obvious that less eutectic can be formed accordins:as the carbon-content of the whole is further below the eutecticratio. In the hyper-eutectic irons the isolated particles of graphitecan exercise but little influence on the formation of the platesof eutectic, whose shape, size, and utter lack of interlacing ac-. FiG. 1.—Ijiprovised Transvekse-Testing Appakatus. count for the poor physical qualities of this kind of iron. Inthe hypo-eutectic irons, on the other hand, a skeleton of aus-tenite, called by Professor Howe primaustenoid, forms first,and, being relatively solid by being well below its freezingpoint at the time of the freezing of the eutectic, can prevent theformation of large plates of the latter, which, if formed, acton the mass as a whole like gigantic cleavage-planes. Thefurther the carbon-content of the whole is below the eutecticratio, the earlier must be the freezing of the austenite, and thegreater its quantity before the formation of the eutectic canbegin. Therefore, the more powerful will it be in preventing 330 EFFECT OF HIGH CARBON ON CHARCOAL-IRON. the formation of the huge plates of eutectic when the eutecticfreezing-point is reached, while the quantity of the latter whichcan form is diminished at a still more rapid rate. If this explanation be correct i
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