He was no beauty – College – pug nose and pock-marked skin; but the romance of the railroads pervaded everything and everyone, and College was the only man for miles around who knew how to manipulate his thoughts about it into words. Jonathan stared at this flesh-and-blood miracle in this place of miracles and was more awed than by all the others put together; he had no idea what the words might mean or even if they had meaning, but the sound of them had the sound of fate. As for College, in the circus that was Denver he played his circus trick with a clown’s delight. He had a clown’s perverse vanity, too; he worked to make his usual audience of silent, dour men laugh out loud and figured that later on, when half-asleep at night, at least one of them was going to fret inwardly at the edge behind the clowning – and yet as everybody knows, it’s only the clown who gives his act a second thought. None of College’s audiences had ever seemed so wholly captivated as this thin recruit, whom he’d watched crossing the yard only moments before with real dismay: so young, so underfed, so unbelievably raw. He laughed, delighted at his own surprise as well as at the boy’s enchanted response. ‘Link and pin must match like husband and wife,’ he went on, swinging on the words now, soaring with them, as though he’d climbed off the floor of the big top and taken to the high-wires above. ‘There’s no room for careless promiscuity here. As always, it’s the gods – in this case, you and I – who will pay the price.’

Twenty years afterwards, Jonathan recorded this speech in his diaries word for word for my computer to grind out, not a single word forgotten in all that time. And catching the words ‘link and pin’ out of this extraordinary medley, he formed link and pin with his hands and rehearsed for College the switchman’s job of coupling one railroad car to another, a technique Mr Finster had demonstrated to him and which he had rehearsed alone night after night with his hands in the darkness of the sod hut, dreaming of this very day but never, not in his wildest imaginings, not ever dreaming of it in such glory as this.

College could hardly believe his luck, too: not only an audience, but a fellow performer at that. He laughed again and clapped his hand on the raw recruit’s shoulder. ‘You’re a great man,’ he said to Jonathan, who had never before in his life had a compliment of any sort. ‘Now I’ll do what I can to teach you: to teach you is to protect you, because the very first lesson of all is that this is dangerous work. When it rains or when the mists come off the mountains in the early morning, one slip of the foot and you’re down beneath the wheels.’

The link-and-pin coupling was an absurd system, as absurd as outside brakes, even more so maybe, cumbersome, unreliable, not just dangerous – College was undercutting it – but ferociously dangerous, stupidly, insanely dangerous. Too many unknowns figure in the equation, just as too many unknowns figure in what’s expected of a newly-freed slave. There were forty different species of couplers – species, not varieties; the varieties were endless. Pins were bent, straight, skewed; all weights, thicknesses, lengths, angles. The fit depended on the load of the train, the grade of the track, the relationship between the two cars – never of the same manufacture, never the same design – an intensely mathematical problem to be solved at breakneck speed without any tools but experience and intuition.