"Our submergence will be two hundred and ten feet," went on Matt. "You and Carl, Clackett, will put the steel baulks in place. I'll have Dick and Gaines help you."
Another order was called to the engine room, and presently there were sounds, forward and aft, which indicated that the metal props, to further strengthen the steel shell, were being dropped into their supports.
"Cassidy," said Matt, "see that the double doors of the hatch are secured."
"Aye, aye, sir," answered the mate, darting up the conning-tower ladder.
"Speake," ordered Matt, through another tube, "see that the tension indicators are in place."
"Double doors of the hatch secured," reported Cassidy a moment later.
"Pressure sponsons in place," came rattling through the tube from Clackett.
"Tension indicators in position," announced Speake.
"Dive at the rate of twelve yards to the minute, Clackett," ordered Matt.
A hiss of air, escaping from the ballast tanks as the water came in, was heard. A tremor ran through the steel fabric, followed by a gentle downward motion. Matt kept his eyes on the manometric needles. Twenty yards, twenty-five, thirty, and forty were indicated. A pressure of ten pounds to the square centimeter was recorded.