"Sylph, ahoy!" shouted Frank, rising.
"What boat's that?" roared Uncle Ben, in reply.
"The Zephyr, of and from Rippleton," returned the coxswain. "Can you tell me what depth of water there is in this passage?"
"Where's your chart?"
"We must have a chart of the lake," suggested Fred.
"That we must. Who shall draw it?"
"Fred Harper."
"We have no chart. Will you give me the depth of water inside the island?" continued Frank.
"Short fathom," replied Uncle Ben.
"We are none the wiser," interposed Charles. "How much is a fathom?"