The layer of coal in contact with the carbonized or silicified part of the specimens is due, then, to a compression of the organic elements already chemically carbonized, but in which the mineral matter was not yet hardened and was able to escape.

So when molten iron is poured into an ordinary sand mould, which has been faced with this refractorily carbonized fabric, it wets every portion of it, tending to absorb the carbon, and doubtless would do so if it remained fluid long enough, but as the metal cools almost immediately, there is no appreciable destruction of the fibers.

Here, again, we have a piece of very fine lace, which has been similarly carbonized, and displays the same qualities of ductility and incombustibility.