Again I experienced a marvellous start: Jonathan Spottiswood was the name of my great-great-uncle, whose unaccountable disappearance from London just a century since had involved our family in so much protracted litigation as to the succession to his property. In fact, it was Jonathan Spottiswood's money which at that moment formed the bulk of my little fortune. But I would not interrupt him, so great was my anxiety to hear the story of his life. "I was born in London," he went on, "in 1750. If you can hear me say that and yet believe that possibly I am not a madman, I will tell you the rest of my tale; if not, I shall go at once and for ever." "I suspend judgment for the present," I answered. "What you say is extraordinary, but not more extraordinary perhaps than the clear anachronism of your ignorance about locomotives in the midst of the present century." "So be it, then. Well, I will tell you the facts briefly in as few words as I can. I was always much given to experimental philosophy, and I spent most of my time in the little laboratory which I had built for myself behind my father's house in the Strand. I had a small independent fortune of my own, left me by an uncle who had made successful ventures in the China trade; and as I was indisposed to follow my father's profession of solicitor, I gave myself up almost entirely to the pursuit of natural philosophy, following the researches of the great Mr. Cavendish, our chief English thinker in this kind, as well as of Monsieur Lavoisier, the ingenious French chemist, and of my friend Dr. Priestley, the Birmingham philosopher, whose new theory of phlogiston I have been much concerned to consider and to promulgate. But the especial subject to which I devoted myself was the elucidation of the nature of fixed air. I do not know how far you yourself may happen to have heard respecting these late discoveries in chemical science, but I dare venture to say that you are at least acquainted with the nature of the body to which I refer." "Perfectly," I answered with a smile, "though your terminology is now a little out of date. Fixed air was, I believe, the old-fashioned name for carbonic acid gas."