e the change I cannot form the foggiest idea. But I should like to
hear your provisional theories on the subject."

"You won't hear them at present. They are mere wild conjectures. But to
resume: what do we do next?"

"Go to New Inn and rake over the deceased gentleman's apartments."

Thorndyke smilingly ignored my answer and continued--

"We examine each explanation in turn and see what follows from it;
whether it agrees with all the facts and leads to the discovery of new
ones, or, on the other hand, disagrees with some facts or leads us to an
absurdity. Let us take a simple example.

"Suppose we find scattered over a field a number of largish masses of
stone, which are entirely different in character from the rocks found in
the neighbourhood. The question arises, how did those stones get into
that field? Three explanations are proposed. One: that they are the
products of former volcanic action; two: that they were brought from a
distance by human agency; three: that they were carried thither from
some distant country by icebergs. Now each of those explanations
involves certain consequences. If the stones are volcanic, then they
were once in a state of fusion. But we find that they are unaltered
limestone and contain fossils. Then they are not volcanic. If they were
borne by icebergs, then they were once part of a glacier and some of
them will probably show the flat surfaces with parallel scratches which
are found on glacier-borne stones. We examine them and find the
characteristic scratched surfaces. Then they have probably been brought
to this place by icebergs. But this does not exclude human agency, for
they might have been brought by men to this place from some other where
the icebergs had deposited them. A further comparison with other facts
would be needed.

"So we proceed in cases like this present one. Of the facts that are
known to us we invent certain explanations. From each of those
explanations we deduce consequences; and if those consequences agree
with new facts, they confirm the explanation, whereas if they disagree
they tend to disprove it. But here we are at our destination."

We turned out of Wych Street into the arched passage leading into New
Inn, and, halting at the half-door of the lodge, perceived a stout,
purple-faced man crouching over the fire, coughing violently. He held up
his hand to intimate that he was fully occupied for the moment, and we
accordingly waited for his paroxysm to s