"And how queer it smells!" exclaimed Hal.
"Sulphur!" ejaculated Grandpa Martin.
He and the children looked at the queer blue fire that seemed to come from inside the rock. What could it mean?
CHAPTER XX
THE HAPPY TRAMP
Grandpa Martin stood looking down at the queer, burning rock. The blue fire was flaming up brighter now, and it made a strange light on the faces of the Curlytops and Hal as they gathered about. The sky was cloudy and it was getting dark.
"Oh, what is it? What is it?" asked Ted and Jan.
"It smells just like old-fashioned sulphur matches that my grandmother used to light," said Nora, who had come out, having seen the queer light from the cook-tent.
"And it is sulphur that is burning," said Grandpa Martin. "That rock has sulphur in it, not gold, Hal. And it is the sulphur that is burning with the blue fire."
"But what makes it?" asked the children.