My name is Anthony Marsden. I am a physician, and formerly resided at Mrs. Brown's house, in Russell Place. Some three or four years ago I found the atmosphere of London beginning to tell upon my health, and determined to remove into the suburbs. I bought a small practice in the neighbourhood of St. John's Wood, and gave up the greater portion of my London patients. I was, however, desirous of not altogether relinquishing that connection, and with this object rented two rooms at Mrs. Brown's, where I might be consulted by such patients as I still retained in that neighbourhood. I used to drive up for this purpose every Monday and Thursday morning. I had been doing this for some time, when the first and second floor apartments were taken by the Baron R**. I did not at first much like him. I thought him an impostor. He seemed, however, to wish to make my acquaintance, and I found that he was, at all events, a very highly informed man on all matters of science. We had frequent conversations respecting mesmerism. He certainly seemed to be himself a believer in it. Were I not myself thoroughly satisfied of its impossibility, I am not at all sure but that he might have convinced me on the subject. I am quite unable to account for many of the phenomena exhibited. They were, however, of course, to be accounted for in some way. He seemed a very excellent chemist, and we used at times to pursue our investigations together. There was a small room at the back of the house, on the basement floor, which he used as a laboratory. He invited me to make use of it, and I was frequently there. He was always engaged in experiments of one kind or another, and had various ingenious projects in hand. In the laboratory was a large assortment of chemicals and medicines of various kinds. In the case of poor patients, I have sometimes asked him to make up a prescription, and he has done so. At the time at which I knew him, he was engaged in a series of experiments on the metals, and more especially on mercury, antimony, lead, and zinc. I think he must have had almost every preparation of these that is made. I believe that his researches were for the purpose of finding a specific against the disease so prevalent among painters, which is known by the name of "lead colic." The laboratory was at the back of the house, and quite detached from all the other rooms. There was an open space between it and the rest of the house, with only a passage communicating with the offices. This passage was shut off by a glass door, and there was a wooden door at the end into the laboratory. Both these doors were always kept closed. They were not usually locked. I told the Baron I thought they should be, but he said no one would go there. He had a weight put on to the laboratory door to close it. The glass door had a spring already. I frequently made use of his laboratory: sometimes when he was absent. I might go there with or without him, whenever I pleased.