ON THE CRYSTALLIZATION OF CAST IRON. 813

Swedish steel irons, the under surface will present smallcrystallized concaves, in which the rudiments of theoctahedron may be found.

English malleable iron, when melted, cools in flat but-tons with a smooth upper and under surface; but whenmelted with from 1 to 2 per cent, of carbon, the coolingbecomes more convex on both sides, and crystallizationensues, in point of form, similar to that which takesplace with foreign iron, but with a less splendid metallicsurface. The grain of the fracture of cast or meltedmalleable iron varies with every change of temperature.If it is melted in a heat merely sufficient for its fusion,the grain will be small and tough, and the iron will drawat a red heat under the hammer. Every shade of heatbeyond this impairs the malleability ; and when meltedin 170° of Wedgewood, it either crystallizes in a scalysort of lamina, or in cubes inserted in each other, not inthe least ductile when cold, or malleable whilst hot.

ILLUSTRATIVE NOTES.Note A.

ON A VARIETY OF CRYSTALLIZED CAST IRON FOUND AT EBBW VALE.

About three years ago, a new variety of crystallized cast iron wasround in the bottom of a blast-furnace at Ebbw Vale, in South Wales,e hearth of which had been in work for ten or fifteen years. Inproceeding to replace the old by a new hearth, a large mass of iron,several tons in weight, was found to have penetrated the false bottoms,an to have filled up all the void spaces of the inferior part of thefurnace.

How long this mass had remained in a state of subsidence, or ex-P ose ^he communication of a very high temperature from the fluidiron, during the continued progress of smelting, in large quantitiesresting upon it, could not be ascertained. It had, however, assumed aregular crystalline structure, in pentagonal curved prisms inserted ineach other. The interior surface colour silvery, and the fracture,