Loud were the exclamations of surprise and delight as the column of water shot up into the air with a boom like a cannon.
"What makes it?" asked Maurice Perry.
"I don't know, I'm sure," said John. "This one always does so after a storm; and one on the other side there spouts and bangs at low tide--the lower the tide the louder she bangs."
Mr. Bernard and the rest of the party had arrived now, and as if for their benefit the horn spouted full eighty feet, dropping the spray in a shower all around them.
"What makes it bang so, Mr. Bernard?" asked Maurice again, not satisfied with John's answer.
"The air driven by a rush of the water, Maurice. There is a hole in the side of that rock, extending up to the surface, and the air rushes through, followed presently by a mass of water, and the escape of the air from its pursuer causes the loud report."
"It is simply a big pop-gun," said Joe, "and it works itself, without any boy's help."
"Oh, I see a rainbow," said Lewis Germaine.
"Where, where?" asked the others.
"Right there in the spray."