808 ON THE CRYSTALLIZATION OF CAST IRON.

coloured crystals were formed, and their attachment toa metallic base, induced me at first to conclude theywere purely metallic. Like the mass found in the fis-sure, they bruised in a mortar, and were equally mag-netic. Several of the crystals in succession were exposedto the action of the blow-pipe at a bright red heat; thegold colour deepened to a green, followed by a blue, andthen successively passing through the usual shades, re-turning always to the tinge of the original ground, likethe copper colour in fine indigo. When exposed to theaction of the blow-pipe on charcoal, the crystals seemedto burn, and emit greenish scintillations with borax;they remained for a great length of time without losingeither colour or form.

As the paper before alluded to contains a particulardetail of the various stages of the crystallization of castiron, and of the method of obtaining it in the large way,it is my intention to forward to you, for the Magazine,a copy of the same; leaving it for you to determine,whether, in the absence of engravings, it is calculated toconvey information to your readers.

The crystallization of cast iron may be divided intotwo classes ; namely, that which takes place in chasmsor shrinkages of the metal, and that which is merelysuperficial. The former possesses the greatest beautyand variety, and may with propriety be divided intothree distinct stages.

1st, That in which crystallization may be said to havecommenced, and which, while confined to this stage,may truly be called linear. This is indicated by a seriesof lines running parallel or concentric to each other,according as the chasm inclines to a plane or hemisphere.These ground lines are intersected at right angles by aslighter class of lines, which has the effect of coveringthe surface of the metal with a chequered series of dotsand minute hollow squares.