The two lamps were now lighted, and the explorations began.
"I think it is advisable," was the Professor's first observation, "that we go in a hundred feet or so, and then mount one of our lamps in a conspicuous place. We can then proceed with the other as far as the water, and if any accident happens it will not cause trouble to both of the lights. We can always have one of them to fall back on."
When they had gone the distance determined on, a secure ledge was selected, and Harry placed the light so it would cast its beams along the cave.
"Be careful now, we are near the water."
The Professor had now the other light, and the boys led the way, so the beams from the light shone past ahead of them. They went beyond the point where the water had been found previously, but there was no sign of it. The course of the cave now changed to the right, and the floor of the cave went downwardly at a slight descent.
The Professor suddenly restrained the boys. "Wait a moment; the light behind us should be brought forward to this point."
George went back and brought it up, and after some delay a place for it was found. The two lights now plainly showed a sudden enlargement in the area of the cave, and above them hung what appeared to be huge icicles, giving the interior a weird appearance. Still no water was in sight.
"The white substances we see all around us indicate that above us the rocks are limestone, and water, in coming through, has acted on the stone so as to form carbonate of lime, or chalk."
The single lamp was now sufficient to light up the interior, which looked like a domed iceberg, with all sorts of fantastic figures standing out in bold relief, which were contrasted by the many dark recesses irregularly scattered about everywhere.
"I see an opening beyond," was Harry's remark, in a suppressed tone.