The sun was setting and turning the rolling Hampshire moor into a wonderful autumnal panorama. The sergeant, with many critical and incredulous glances, which showed his deep doubts of the sanity of my companion, lurched along beside us. As we approached the scene of the crime I could see that my friend under all his habitual coolness was in truth deeply agitated.

“Yes,” he said in answer to my remark, “you have seen me miss my mark before, Watson. I have an instinct for such things, and yet it has sometimes played me false. It seemed a certainty when first it flashed across my mind in the cell at Winchester, but one drawback of an active mind is that one can always conceive alternative explanations which would make our scent a false one. And yet - and yet - - Well, Watson, we can but try.”

As he walked he had firmly tied one end of the string to the handle of the revolver. We had now reached the scene of the tragedy. With great care he marked out under the guidance of the policeman the exact spot where the body had been stretched. He then hunted among the heather and the ferns until he found a considerable stone. This he secured to the other end of his line of string, and he hung it over the parapet of the bridge so that it swung clear above the water. He then stood on the fatal spot, some distance from the edge of the bridge, with my revolver in his hand, the string being taut between the weapon and the heavy stone on the farther side.

“Now for it!” he cried.

At the words he raised the pistol to his head, and then let go his grip. In an instant it had been whisked away by the weight of the stone, had struck with a sharp crack against the parapet, and had vanished over the side into the water. It had hardly gone before Holmes was kneeling beside the stonework, and a joyous cry showed that he had found what he expected.

“Was there ever a more exact demonstration?” he cried. “See, Watson, your revolver has solved the problem!” As he spoke he pointed to a second chip of the exact size and shape of the first which had appeared on the under edge of the stone balustrade.

“We’ll stay at the inn to-night,” he continued as he rose and faced the astonished sergeant. “You will, of course, get a grappling-hook and you will easily restore my friend’s revolver. You will also find beside it the revolver, string and weight with which this vindictive woman attempted to disguise her own crime and to fasten a charge of murder upon an innocent victim. You can let Mr. Gibson know that I will see him in the morning, when steps can be taken for Miss Dunbar’s vindication.”

Late that evening, as we sat together smoking our pipes in the village inn, Holmes gave me a brief review of what had passed.

“I fear, Watson,” said he, “that you will not improve any reputation which I may have acquired by adding the case of the Thor Bridge mystery to your annals. I have been sluggish in mind and wanting in that mixture of imagination and reality which is the basis of my art. I confess that the chip in the stonework was a sufficient clue to suggest the true solution, and that I blame myself for not having attained it sooner.