It may be that the police resented the intrusion of an amateur, or that they imagined themselves to be upon some hopeful line of investigation; but it is certain that we heard nothing from them for the next two days. During this time Holmes spent some of his time smoking and dreaming in the cottage; but a greater portion in country walks which he undertook alone, returning after many hours without remark as to where he had been. One experiment served to show me the line of his investigation. He had bought a lamp which was the duplicate of the one which had burned in the room of Mortimer Tregennis on the morning of the tragedy. This he filled with the same oil as that used at the vicarage, and he carefully timed the period which it would take to be exhausted. Another experiment which he made was of a more unpleasant nature, and one which I am not likely ever to forget. "You will remember, Watson," he remarked one afternoon, "that there is a single common point of resemblance in the varying reports which have reached us. This concerns the effect of the atmosphere of the room in each case upon those who had first entered it. You will recollect that Mortimer Tregennis, in describing the episode of his last visit to his brother's house, remarked that the doctor on entering the room fell into a chair? You had forgotten? Well I can answer for it that it was so. Now, you will remember also that Mrs. Porter, the housekeeper, told us that she herself fainted upon entering the room and had afterwards opened the window. In the second case--that of Mortimer Tregennis himself--you cannot have forgotten the horrible stuffiness of the room when we arrived, though the servant had thrown open the window. That servant, I found upon inquiry, was so ill that she had gone to her bed. You will admit, Watson, that these facts are very suggestive. In each case there is evidence of a poisonous atmosphere. In each case, also, there is combustion going on in the room--in the one case a fire, in the other a lamp. The fire was needed, but the lamp was lit--as a comparison of the oil consumed will show--long after it was broad daylight. Why? Surely because there is some connection between three things--the burning, the stuffy atmosphere, and, finally, the madness or death of those unfortunate people. That is clear, is it not?" "It would appear so."