"Clear water to the left of us," he reported.
"Too close ashore?" asked the Doctor.
"I think not," was Dave's answer. "We'll have to submerge for three or four miles; then we'll be clear of the ice."
Signal bells clanged, and again they were gliding under the ocean's armor of ice.
As he listened to the hum of the machinery, one question puzzled Dave. He had seen something along the end of that ice-floe. What was it? A sail? If so, it was a very strange one—half white and half black. He could not be sure it was a sail. But what else could it have been?
But now they had swept out from under the ice. It was time to rise. Instantly he pressed the button. The craft slowed again. Another press, and as before they rose. This time no white surface would interrupt them. A current coming from land caught them forward and tilted the craft. She slanted from fore to aft. This did not matter; she would right herself on the surface like a cork.
But what was this? As the point shot from the water, something rang out against the steel. This was followed immediately by what, in the narrow apartments, amounted to a deafening explosion; then came the sound of rushing waters.
"Great God! We're bombed!" shouted the Doctor.
Dave's cool head saved them for the moment. His hand seized an electric switch and he pulled it desperately. The bow compartment was quickly closed, checking the rush of water into the rest of the "sub," Fortunately, no one had been forward at the time.
But now they were sinking rapidly. Then came the throb of the pumps forcing out the water from the compartments aft. Slowly the sickening sinking of their ship was checked.