"Is it water you are digging for, Mr. Parry?" asked Professor Zepplin.
But the guide did not hear the question. He was too busy with his mining operations at the moment.
"Come on, boys," he urged. "Get busy here."
"At what?" asked Ned. "We're with you, but we don't know what you want us to do."
"Yes; can we help you?" inquired Tad.
"Of course you can. Get those other shovels and dig."
"Where?"
"Right here. Make the dirt fly as fast as you want to. I'll show you something in a minute."
He did. All at once the sand beneath them gave way, and the Pony Rider Boys, all except Stacy Brown, uttered a yell as they sank waist deep into a sink of soft, wet sand.
Parry had felt the sand giving way, and with a warning had leaped from the hole. The lads had not been quick enough.