“I can’t imagine,” said I, “that you have absolutely nothing in view.  That you are going to this place with no defined purpose whatever.”

“I did not say exactly that,” replied Thorndyke.  “I said that I was not going to look for any particular thing or fact.  I am going in the hope that I may observe something that may start a new train of speculation.  But that is not all.  You know that an investigation follows a certain logical course.  It begins with the observation of the conspicuous facts.  We have done that.  The facts were supplied by Marchmont.  The next stage is to propose to oneself one or more provisional explanations or hypotheses.  We have done that, too—­or, at least I have, and I suppose you have.”

“I haven’t,” said I.  “There is Jeffrey’s will, but why he should have made 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.”