“We shall know that he had them with him,” he replied. “Though, of course, if we don’t find them, that will not prove that they are not here. Still, I think we should try to settle the question.” His answer left me quite unconvinced; but the care with which he searched the ditch and sorted out the weed left me in no doubt that, to him, the matter seemed to be of some importance. However, nothing came of the search. If the keys were there they were buried in the mud, and eventually we had to give up the search and make our way back towards the station. As we passed out of the lane into Ponder’s Road, Thorndyke stopped at the entrance, under the trees, by a little triangle of turf which marked the beginning of the lane, and looked down at the muddy ground. “Here is quite an interesting thing, Jervis,” he remarked, “which shows us how standardized objects tend to develop an individual character. These are the tracks of a car, or more probably a tradesman’s van, which was fitted with Barlow tyres. Now there must be thousands of vans fitted with these tyres; they are the favourite type for light covered vans, and when new they are all alike and indistinguishable. Yet this tyre--of the off hind-wheel--has acquired a character which would enable one to pick it out with certainty from ten thousand others. First, you see, there is a deep cut in the tyre at an angle of forty-five, then a kidney-shaped ‘Blakey’ has stuck in the outer tyre without puncturing the inner; and finally some adhesive object--perhaps a lump of pitch from a newly-mended road--has become fixed on just behind the ‘Blakey.’ Now, if we make a rough sketch of those three marks and indicate their distance apart, thus”--here he made a rapid sketch in his note-book, and wrote in the intervals in inches--“we have the means of swearing to the identity of a vehicle which we have never seen.” “And which,” I added, “had for some reason swerved over to the wrong side of the road. Yes, I should say that tyre is certainly unique. But surely most tyres are identifiable when they have been in use for some time.” “Exactly,” he replied. “That was my point. The standardized thing is devoid of character only when it is new.” It was not a very subtle point, and as it was fairly obvious I made no comment, but presently reverted to the case of Pedley deceased. “I don’t quite see why you are taking all this trouble. The insurance claim is not likely to be contested. No one can prove that it was a case of suicide, though I should think no one will feel any doubt that it was, at least that is my own feeling.” Thorndyke looked at me with an expression of reproach. “I am afraid that my learned friend has not been making very good use of his eyes,” said he. “He has allowed his attention to be distracted by superficial appearances.” “You don’t think that it was suicide, then?” I asked, considerably taken aback.