I sat down at the table and produced a couple of glass flasks, tightly corked.

“Here you are,” I said.  “This is ordinary gunpowder, and this other one’s my stuff.  It looks harmless enough, doesn’t it?”

Joyce took both flasks and examined them with interest.  “You’ve not brought very much of it,” she said.  “I was hoping we were going to have a really big blow-up.”

“It will be big enough,” I returned consolingly, “unless I’ve made a mistake.”

“Where are you going to do it?” she asked.

“Somewhere at the back of Canvey Island,” I said.  “There’s no one to wake up there except the sea-gulls, and we can be out of sight round the corner before it explodes.  I’ve got about twenty feet of fuse, which will give us at least a quarter of an hour to get away in.”

“What fun!” exclaimed Joyce.  “I feel just like an anarchist or something; and it’s lovely to know that one’s launching a new invention.  We ought to have kept that bottle of champagne to christen it with.”

“Yes,” I said regretfully; “it was the real christening brand too.”

There was a short silence.  “I’ve thought of a name for it,” cried Joyce suddenly.  “The powder, I mean.  We’ll call it Lyndonite.  It sounds like something that goes off with a bang, doesn’t it?”

I laughed.  “It would probably suggest that to the prison authorities,” I said.  “Anyhow, Lyndonite it shall be.”

We finished breakfast, and going up on deck I proceeded to haul in the anchor, while Joyce stowed away the crockery and provisions below.  For once in a way the engine started without much difficulty, and as the tide was running out fast it didn’t take us very long to reach the mouth of the creek.

Once outside, I set a course down stream as close to the northern shore as I dared go.  Except for a rusty-looking steam tramp we had the whole river to ourselves, not even a solitary barge breaking the long stretch of grey water.  One by one the old landmarks—­Mucking Lighthouse, the Thames Cattle Wharf, and Hole Haven—­were left behind, and at last the entrance to the creek that runs round behind Canvey Island came into sight.

One would never accuse it of being a cheerful, bustling sort of place at the best of times, but at five o’clock in the morning it seemed the very picture of uninhabited desolation.  A better locality in which to enjoy a little quiet practice with new explosives it would be difficult to imagine.

I navigated the Betty in rather gingerly, for it was over three years since I had visited the spot.  Joyce kept on sounding diligently with the lead either side of the boat, and at last we brought up in about one and a half fathom, just comfortably out of sight of the main stream.

“This will do nicely,” I said.  “We’ll turn her round first, and then I’ll row into the bank and fix things up under that tree over there.  We can be back in the river before anything happens.”