every portion of the zinc, or, as we say, it amalgamates with the zinc.
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.

The casting which I shall now exhibit represents a very interesting and
novel experiment. In this case, the piece of lace, having open meshes a
little larger than a pin's head, instead of being laid upon one face of
the mould, was suspended in it in such a way as to divide it into two
equal parts. Two gates or runners were provided, leading from the
"sinking head" to the bottom of the mould, one on each side of the lace
partition. The molten iron was poured into the sinking head, and flowing
equally through both runners, filled the mould to a common level. The
lace, which was held in position by having its edges embedded in the
walls of the mould, remained intact. When the casting was cold, it was
thrown upon the floor of the foundry and separated into two parts, while
the lace fell out uninjured, and the pattern was found to be reproduced
upon each face of the casting.

The question naturally arises, Why did not the iron run through the
holes and join together? The answer may be found in the fact that the
thin film of oxide of iron, or "skin," as it is popularly called, which
always forms on the surface of molten iron, was caught in these fine
meshes, and thus prevented the molten metal from joining through the
holes. I have repeated the experiment a number of times, and find that
the meshes must be quite small (not over one fiftieth of an inch),
otherwise the metal will reunite.

I think that this observation explains the cause of many obscure flaws
found in castings, sometimes causing them to break when subjected to
quite moderate strains. We frequently find little "cold shot," or
metallic globules, embedded in cast iron or steel, impairing the
strength of the metal, and it has long been asked, "What is the cause of
this defect?" The pellicles have been carefully analyzed, under the
supposition that they might be alloys of iron and nickel, or some other
refractory metal, but the analysis has failed to substantiate this
theory. Is it not probable that in the process of casting, little drops
of molten metal are somet