"What does it do then?"
"Then," said Frank slowly, "it must go along on top of the rock or clay."
"When does it come out of the ground?"
"Oh, I see! The rain goes down until it comes to that lime rock. Then it goes along the rock, and comes out there," said Donald, pointing to the spring.
"Does it always?" asked Frank. "I have read of very deep wells that are bored down into the ground more than a thousand feet, and when the augur strikes water the water comes right up to the top of the ground."
"You are talking about artesian wells," said Uncle Robert.
"Yes, that is the name."
[Illustration: Section of hillside.]
They had left the spring and were walking down toward the mouth of the creek. The rain had swollen the little stream, and the water was dark with dirt.
"See how muddy the water is," said Susie.