“Hey, you landsmen, do you know a buoy from an umbrella!”

“Do you know the difference between a Sunday-school text and petty larceny?” retorted Jack Benson, sternly.  “What do you mean by taking the submarine without leave?”

“I’ve been experimenting—­flirting with science,” responded Eph, loftily.  “Say, if you landsmen know a buoy from a banana, get down to the bow moorings of this steel mermaid, and I’ll pass you the bow cable.  It’s a heap easier to lead this submarine horse out of the stall, single-handed, than it is to take him back and tie him.”

Hal rowed easily to the buoy, while Eph, returning to the steering wheel and the tower controls, ran the “Farnum,” with just bare headway, up to where he could toss the bow cable to those waiting in the boat.  A few moments later the stern cable, also, was made fast, in such a way as to allow a moderate swing to the bulky steel craft.

“Now, you can take me ashore, if you feel like it,” proposed Eph, standing on the platform deck.

“Not quite yet,” returned Skipper Jack, though the small boat lay alongside.  “We’ve got some inspecting to do.  But how did you get on board in the first place?”

“Why, the night watchman was in the yard for a few minutes, and I got him to put me on board.  I figured I could hail somebody else when I was ready to go on shore.”

“But what on earth made you do such a thing?” demanded Captain Jack, in a low tone.  “It’s really more than you had a right to do, Eph, without getting Mr. Farnum’s permission.”

“Why, I’ve known you to take the ‘Pollard’ and try something when Mr. Farnum wasn’t about,” retorted Somers, looking surprised.

“You never knew me to do it when I could ask permission, although, as captain, I have the right to handle the boat.  But that leave doesn’t extend to all the rest, Eph.  What were you doing down there, anyway?”

“Why, I came on board, and left the manhole open for ten minutes,” answered Somers.  “Then I found the cabin thermometer standing at 49 degrees.  I wondered how much warmth could be gained by going below the surface I had been down an hour and five minutes when you began to signal with that sledgehammer—­”

“Sounding-lead,” Jack corrected him.

“Well, it sounded like a sledge-hammer, anyway,” grinned young Somers.  “While I was down below I found that the temperature rose four degrees.”

“Part of that was likely due to the warmth of your body, and the heat of the breath you gave off,” hinted Benson.

“You could have gotten it up to eighty or ninety degrees by turning on the electric heater far enough,” suggested Hal.

“I wanted to see whether it would be warmer in the depths; wanted to find out how low I could go and be able to do without heat in winter,” Somers retorted.

“I could have told you that, from my reading, without any experiment,” retorted Skipper Jack.  “Close your conning tower and go down a little way, and the temperature would gradually rise a few degrees.  That’s because of the absence of wind and draft.  But, if you could go down very, very deep without smashing the boat under the water pressure, you’d find the temperature falling quite a bit.”