I gazed at my friend in blank astonishment, for these events befell in the days before I had joined him as his assistant, and his special knowledge and powers of inference were not then fully appreciated by me.
"It is clear, Thorndyke," I said, "that footprints have a very different meaning to you from what they have for me. I don't see in the least how you have reached any of these conclusions."
"I suppose not," was the reply; "but, you see, special knowledge of this kind is the stock-in-trade of the medical jurist, and has to be acquired by special study, though the present example is one of the greatest simplicity. But let us consider it point by point; and first we will take this set of footprints which I have inferred to be a fisherman's. Note their enormous size. They should be the footprints of a giant. But the length of the stride shows that they were made by a rather short man. Then observe the massiveness of the soles, and the fact that there are no nails in them. Note also the peculiar clumsy tread--the deep toe and heel marks, as if the walker had wooden legs, or fixed ankles and knees. From that character we can safely infer high boots of thick, rigid leather, so that we can diagnose high boots, massive and stiff, with nailless soles, and many sizes too large for the wearer. But the only boot that answers this description is the fisherman's thigh-boot--made of enormous size to enable him to wear in the winter two or three pairs of thick knitted stockings, one over the other. Now look at the other footprints; there is a double track, you see, one set coming from the sea and one going towards it. As the man (who was bow-legged and turned his toes in) has trodden in his own footprints, it is obvious that he came from the sea, and returned to it. But observe the difference in the two sets of prints; the returning ones are much deeper than the others, and the stride much shorter. Evidently he was carrying something when he returned, and that something was very heavy. Moreover, we can see, by the greater depth of the toe impressions, that he was stooping forward as he walked, and so probably carried the weight on his back. Is that quite clear?"
"Perfectly," I replied. "But how do you arrive at the interval of time between the visits of the two men?"