Leithen seemed disinclined for further exercise. He lit a pipe and smoked quietly for a little. "Odd that you didn't know Hollond. You must have heard his name. I thought you amused yourself with metaphysics." Then I remembered. There had been an erratic genius who had written some articles in Mind on that dreary subject, the mathematical conception of infinity. Men had praised them to me, but I confess I never quite understood their argument. "Wasn't he some sort of mathematical professor?" I asked. "He was, and, in his own way, a tremendous swell. He wrote a book on Number which has translations in every European language. He is dead now, and the Royal Society founded a medal in his honour. But I wasn't thinking of that side of him." It was the time and place for a story, for the pony would not be back for an hour. So I asked Leithen about the other side of Hollond which was recalled to him by Correi na Sidhe. He seemed a little unwilling to speak... "I wonder if you will understand it. You ought to, of course, better than me, for you know something of philosophy. But it took me a long time to get the hang of it, and I can't give you any kind of explanation. He was my fag at Eton, and when I began to get on at the Bar I was able to advise him on one or two private matters, so that he rather fancied my legal ability. He came to me with his story because he had to tell someone, and he wouldn't trust a colleague. He said he didn't want a scientist to know, for scientists were either pledged to their own theories and wouldn't understand, or, if they understood, would get ahead of him in his researches. He wanted a lawyer, he said, who was accustomed to weighing evidence. That was good sense, for evidence must always be judged by the same laws, and I suppose in the long-run the most abstruse business comes down to a fairly simple deduction from certain data. Anyhow, that was the way he used to talk, and I listened to him, for I liked the man, and had an enormous respect for his brains. At Eton he sluiced down all the mathematics they could give him, and he was an astonishing swell at Cambridge. He was a simple fellow, too, and talked no more jargon than he could help. I used to climb with him in the Alps now and then, and you would never have guessed that he had any thoughts beyond getting up steep rocks. "It was at Chamonix, I remember, that I first got a hint of the matter that was filling his mind. We had been taking an off-day, and were sitting in the hotel garden, watching the Aiguilles getting purple in the twilight. Chamonix always makes me choke a little-it is so crushed in by those great snow masses. I said something about it--said I liked the open spaces like the Gornegrat or the Bel Alp better. He asked me why: if it was the difference of the air, or merely the wider horizon? I said it was the sense of not being crowded, of living in an empty world. He repeated the word 'empty' and laughed.