There is no way of combating this sort of thing, and so I sat down, and he went on:
“It is perfectly simple....” He passed his hand over his forehead. “It is so simple that one would say it must have been thought of before; but that is what is always said of a great invention.... Now I have here” (and he opened out his foolscap) “the full details. But I will not read them to you; I will summarize them briefly.”
“Have you a plan or anything I could watch?” said I a little anxiously.
“No,” he answered sharply, “I have not, but if you like I will draw a rough sketch as I go along upon the margin of your newspaper.”
“Thank you,” I said.
He drew the newspaper towards him and put it on his knee. He pulled out a pencil; he held the foolscap up before his eye, and he began to describe.
“The general principle upon which my speedometer reposes,” he said solemnly, “is the coordination of the cylinder and the cone upon an angle which will have to be determined in practice, and will probably vary for different types. But it will never fall below 15 nor rise over 43.”
“I should have thought——” I began, but he told me I could not yet have grasped it, and that he wished to be more explicit.
“On a king bolt,” he said, occasionally consulting his notes, “runs a pivot in bevel which is kept in place by a small hair-spring, which spring fits loosely on the Conkling Shaft.”
“Exactly,” said I, “I see what is coming.”