It was this:

ASTOR HOUSE

"The inscription is Old English," he said. "'House' signified a
dwelling, but the word 'Astor' I know not. It was probably the name of
a deity, and here was his temple."

This was encouraging, and we looked about eagerly for other signs.

Our steps soon brought us into another street, and as we walked I
expressed my surprise at the wonderful preservation of the stone work,
which looked as though cut but yesterday.

"In such an atmosphere decay is slow," said Nofuhl. "A thousand years
at least have passed since these houses were occupied. Take yonder
oak, for instance; the tree itself has been growing for at least a
hundred years, and we know from the fallen mass beneath it that
centuries had gone by before its birth was possible."

He stopped speaking, his eyes fixed upon an inscription over a
doorway, partly hidden by one of the branches of the oak.

Turning suddenly upon me with a look of triumph, he exclaimed:

"It is ours!"

"What is ours?" I asked.

"The knowledge we sought;" and he pointed to the inscription,