The impression came from a spot not more than an inch wide.

I went carefully over the entire convexity, and six times more the chill ran through my arm.

There were seven circles an inch wide in the curved place, each of which communicated the precise sensation I have described.

The convexity on the opposite side of the slab gave exactly the same results.

But no amount of touching or of pressing these spots singly or in any combination gave the slightest promise of motion to the slab itself.
"'And yet--they're what open it,' said Stanton positively.
"'Why do you say that ?' I asked.
"'I--don't know,' he answered hesitatingly.