6."
Polton now took possession of the hat, and, having stuck a band of wet
tissue-paper round the inside, mixed a small bowl of plaster-of-Paris,
and very dexterously ran a stream of the thick liquid on to the
tissue-paper, where it quickly solidified. A second and third
application resulted in a broad ring of solid plaster an inch thick,
forming a perfect mould of the inside of the hat, and in a few minutes
the slight contraction of the plaster in setting rendered the mould
sufficiently loose to allow of its being slipped out on to a board to
dry.
We were none too soon, for even as Polton was removing the mould, the
electric bell, which I had switched on to the laboratory, announced a
visitor, and when I went down I found a police-sergeant waiting with a
note from Superintendent Miller, requesting the immediate transfer of
the hat.
"The next thing to be done," said Thorndyke, when the sergeant had
departed with the bandbox, "is to measure the thickness of the hairs,
and make a transverse section of one, and examine the dust. The section
we will leave to Polton--as time is an object, Polton, you had better
imbed the hair in thick gum and freeze it hard on the microtome, and be
very careful to cut the section at right angles to the length of the
hair--meanwhile, we will get to work with the microscope.
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