can be for."
"H'm," grunted Thorndyke, as he sauntered up and down the room, teacup in hand, "to guess, eh? I like not that word 'guess' in the mouth of a man of science. What do you mean by a 'guess'?"
His manner was wholly facetious, but I professed to take his question seriously, and replied—
"By a guess, I mean a conclusion arrived at without data."
"Impossible!" he exclaimed, with mock sternness. "Nobody but an utter fool arrives at a conclusion without data."
"Then I must revise my definition instantly," I rejoined. "Let us say that a guess is a conclusion drawn from insufficient facts."
"That is better," said he; "but perhaps it would be better still to say that a guess is a particular and definite conclusion deduced from facts which properly yield only a general and indefinite one. Let us take an instance," he continued. "Looking out of the window, I see a man walking round Paper Buildings. Now suppose I say, after the fashion of the inspired detective of the romances, 'That man is a stationmaster or inspector,' that would be a guess. The observed facts do not yield the conclusion, though they do warrant a conclusion less definite and more general."
"You'd have been right though, sir!" exclaimed Polton, who had stepped forward with me to examine the unconscious subject of the demonstration. "That gent used to be the stationmaster at Camberwell. I remember him well."
The little man was evidently greatly impressed.
"I happen to be right, you see," said Thorndyke; "but I might as easily have been wrong."
"You weren't though, sir," said Polton. "You spotted him at a glance."
In his admiration of the result he cared not a fig for the correctness of the means by which it had been attained.
"Now why do I suggest that he is a stationmaster?" pursued Thorndyke, disregarding his assistant's comment.
"I suppose you were looking at his feet," I answered. "I seem to have noticed that peculiar, splay-footed gait in stationmasters, now that you mention it."
"Quite so. The arch of the foot has given way; the plantar ligaments have become stretched and the deep calf muscles weakened. Then, since bending of the weakened arch causes discomfort, the feet have become turned outwards, by which the bending of the foot is reduced to a minimum; and as the left foot is the more flattened, so it is turned out more than the right. Then the turning out of the toes causes the legs to splay outward from the knees downwards—a very conspicuous condition in a tall man like this one—and you notice that the left leg splays out more than the other.
"But we know that depression of the arch of the foot is brought about by standing for long periods. Continuous pressure on a living structure weakens it, while intermittent pressure strengthens it; so the man who stands on his feet continuously develops a flat instep and a weak calf, while the professional dancer or runner acquires a high instep and a strong calf. Now there are many occupations which involve prolonged standing and so induce the condition of flat foot: waiters, hall-porters, hawkers, policemen, shop-walkers, salesmen, and station officials are examples. But the waiter's gait is characteristic—a quick, shuffling walk which enables him to carry liquids without spilling them. This man walks with a long, swinging stride; he is obviously not a waiter. His dress and appearance in general exclude the idea of a hawker or even a hall-porter; he is a man of poor physique and so cannot be a policeman. The shop-walker or salesman is accustomed to move in relatively confined spaces, and so acquires a short, brisk step, and his dress tends to rather exuberant smartness; the station official patrols long platforms, often at a rapid pace, and so tends to take long strides, while his dress is dignified and neat rather than florid. The last-mentioned characteristics, you see, appear in the subject of our analysis; he agrees with the general description of a stationmaster. But if we therefore conclude that he is a stationmaster, we fall into the time-honoured fallacy of the undistributed middle term—the fallacy that haunts all brilliant guessers, including the detective, not only of romance, but too often also of real life. All that the observed facts justify us in inferring is that this man is engaged in some mode of life that necessitates a good deal of standing; the rest is mere guess-work."
"It's wonderful," said Polton, gazing at the now distant figure; "perfectly wonderful. I should never have known he was a stationmaster." With this and a glance of deep admiration at his employer, he took his departure.
"You will also observe," said Thorndyke, with a smile, "that a fortunate guess often brings more credit than a piece of sound reasoning with a less striking result."
"Yes, that is unfortunately the case, and it is certainly true in the present instance. Your reputation, as far as Polton is concerned, is now firmly established even if it was not before. In his eyes you are a wizard from whom nothing is hidden. But to return to these little pieces, as I must call them, for the lack of a better name. I can form no hypothesis as to their use. I seem to have no 'departure,' as the nautical phrase goes, from which to start an inquiry. I haven't even the material for guess-work. Ought I to be able to arrive at any opinion on the subject?"
Thorndyke picked up one of the pieces, fingering it delicately and inspecting with a critical eye the flat base on which it stood, and reflected for a few moments.
"It is easy to trace a connection when one knows all the facts," he said at length, "but it seems to me that you have the materials from which to form a conjecture. Perhaps I am wrong, but I think, when you have had more experience, you will find yourself able to work out a problem of this kind. What is required is constructive imagination and a rigorous exactness in reasoning. Now, you are a good reasoner, and you have recently shown me that you have the necessary imagination; you merely lack experience in the use of your faculties. When you learn my purpose in having these things made—as you will before long—you will probably be surprised that their use did not occur to you. And now let us go forth and take a brisk walk to refresh ourselves (or perhaps I should say myself) after the day's labour.
The Ambush
"I am going to ask for your collaboration in another case," said Thorndyke, a day or two later. "It appears to be one of suicide, but the solicitors to the 'Griffin' office have asked me to go down to the place, which is in the neighbourhood of Barnet, and be present at the post-mortem and the inquest. They have managed to arrange that the inquest shall take place directly after the post-mortem, so that we shall be able to do the whole business in a single visit."
"Is the case one of any intricacy?" I asked.
"I don't think so," he answered. "It looks like a common suicide; but you can never tell. The importance of the case at present arises entirely from the heavy insurance; a verdict of suicide will mean a gain of ten thousand pounds to the 'Griffin,' so, naturally, the directors are anxious to get the case settled and not inclined to boggle over a little expense."
"Naturally. And when will the expedition take place?" I asked.
"The inquest is fixed for to-morrow—what is the matter? Does that fall foul of any arrangement of yours?"
"Oh, nothing of any importance," I replied hastily, deeply ashamed of the momentary change of countenance that my friend had been so quick to observe.
"Well, what is it?" persisted Thorndyke. "You have got something on."
