"Now, here is another. You can see that it is radically different
from the first, which was from the cartridge used in killing poor
Rena Taylor. This second one is from that gun which I found on the
tenement roof this morning. It lacks the L mark as well as the
concentric circles. Here is another. Its chief characteristics are
a series of pits and elevations which, examined under the
microscope and measured, will be found to afford a set of
characters utterly different from those of any other hammer.
"In short," he concluded with an air of triumph, "the ends of
firing pins are turned and finished in a lathe by the use of tools
designed for that purpose. The metal tears and works unevenly so
that microscopical examination shows many pits, lines, circles,
and irregularities. The laws of chance are as much against two of
these firing pins or hammers having the same appearance under the
microscope as they are against the thumb prints of two human
subjects being identical."
I picked up the curious little arrangement which we had found in
the drawer in Forbes' room and examined it closely.
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