"I said Nature."

"Well, human nature's a part of Nature; and, if you ask me, I should say a careless cook and a foul kitchen chimney—the fire engine up, and a month's notice."

"I do wish you'd be serious. But you've hit it all the same. Half-consumed carbon——"

"You mean soot?"

"Soot is half-consumed carbon. That's the stuff we want. It's the very thing, because a steamship produces loads of it every day. All you want is a suitable apparatus and what you may call a firing charge. I'll just make a note."

He took out his note-book, and wrote in his very neat handwriting the following tabular statement:

SMOKE MACHINE.

REQUIRED.

1. Soot.
2. Combustibles.
3. Receptacle.
4. Vehicle.

"Four-wheelers are cheap, but bang goes your tenner, Bobby," said Eves, looking over his shoulder. "Can't you do without the vehicle?"