When the lamp was in order he held it close to the wall and conducted a systematic survey.

The geological fault which favored the construction of the tunnel seemed to diverge to the left at the further end.

The "face" of the rock exhibited the marks of persistent labor.

The stone had been hewn away by main force when the dislocation of strata ceased to be helpful.
His knowledge was limited on the subject, yet Jenks believed that the material here was a hard limestone rather than the external basalt.
Searching each inch with the feeble light, he paused once, with an exclamation.
"What is it ?" cried Iris.
"I cannot be certain," he said, doubtfully.

"Would you mind holding the lamp whilst I use a crowbar ?" In the stone was visible a thin vein, bluish white in color.