‘That’s right,’ said Doc Kates, looking at Collis warily.

Collis looked right back at him. ‘Supposing someone was to bring these three ingredients — which aren’t illegal when they’re brought into the state of California separately — supposing someone was to bring them up the mountain, just as they are, and then supposing someone was to mix them together right up by the tunnel we’re blasting out and give us a ready supply of the stuff?’

Doc Kates took off his spectacles. His eyes were watery and pale, faded by years of Sierra sun and years of Sierra snow.

‘You’re asking me to do it?’ he wanted to know.

‘Only if you’re willing.’

‘It’s pretty volatile stuff. One mistake and you’re a damned sight higher in the air than Summit Pass.’

‘You’re a careful man.’

‘Yes, I guess you could say that I am.’

‘Then you’ll do it?’

‘Let’s have ourselves a cup of coffee first,’ Doc Kates said. ‘Do you fancy a ginger cookie? I’ve a fresh-baked batch in from Mrs Elias.’

Collis stood up, pushing back his chair. ‘I don’t have much time, Doc. That tunnel has to be bored, and bored quick.’

Doc Kates frowned at him. ‘All right,’ he said, slowly bringing the cups to the table and setting them down. ‘All right, I’ll do it. Do you have time for a cup of coffee now?’

All during the long summer of 1867, the tree-lined mountains below Summit Pass shook and echoed with the sound of explosions. Inside the solid granite tunnel, it was stifling and dusty and intolerably hot, but the Chinese blasters drilled incessantly into the rock face, laid their charges of freshly-brewed nitroglycerin, and gradually blew the inside of the mountains out.

Collis had to return to Sacramento in late July to tidy up months of neglected business; but in mid-August he came back to the Sierras again in a rather rudimentary private passenger car pulled by the City of Sacramento. He climbed down a few hundred feet away from the entrance to the west portal of the Summit Tunnel, and Charles came across to greet him.

‘How’s it going?’ Collis asked. ‘Have we licked this goddam mountain range yet?’

‘You came just in time,’ said Charles. ‘We’re drilling the last of the charge holes right now, and we reckon the two headings should meet up this afternoon. I sent a couple of Chinese foremen back to bring some champagne.’

He followed Charles into the tunnel, and together they walked uphill through the gritty dust of drilled-out granite and the deafening clamour of sledgehammers. Collis took off his hat to wipe the grimy sweat from his forehead with his handkerchief, and coughed.

They arrived at last at the face of the west heading, where thirty or forty blue-pyjama’d Chinese workers were drilling at the granite with hand drills. The white foreman, with his tall cowboy-style hat and drooping moustache, came across and said, ‘Good morning, Mr Edmonds. We should be ready for blasting in a half hour or so. Then you’ll be able to see daylight all the way up to the summit.’