CHAPTER VIII
THE MUD BANK
"What's that noise?" asked Mr. Hardley.
Mr. Hardley, Tom Swift, Mr. Damon, Ned Newton, Koku, and one or twonavigating officers of the craft, were gathered in the operating cabinof the M. N. 1.
"That's water being pumped into the tanks," explained Tom. "We are nowgoing down. If you'll watch the depth gauge you can note our progress."
"Going down, are we?" remarked Mr. Hardley. "Well, it's interesting tosay the least," and he observed the gauge, which showed them to betwenty feet under the surface.
"Bless my hydrometer, but he's got nerve for a first trip in asubmarine! He's all right, isn't he?" whispered Mr. Damon to Tom.
"Well, I'm glad to see he isn't nervous," remarked Tom, honest enoughto give his visitor credit for what was due him. And indeed many aperson is nervous going down in a submarine for the first time. "Stillwe can't go more than thirty feet down in this water," went on Tom. "Abetter test will be when we get about five hundred feet below thesurface. That's a real test, though as far as knowing it is concerned,a person can't tell ten feet from ten hundred in a submarine underwater, unless he watches the gauge."
"Well, I think you'll find Mr. Hardley all right," said Mr. Damon, whoseemed to have taken a strong liking to his new friend.
Certainly the latter showed no signs of nervousness as the craft slowlysettled to the proper depth. He asked numberless questions, showing hisinterest in the operation of the M. N. 1, but he showed not the leastsign of fear. However, as Tom said, that might come later.
"We are going down now," Tom explained, as he pointed out to Mr.Hardley the various controlling wheels and levers, "by filling ourballast tanks with water. We can rise, when needful, by forcing outthis water by means of compressed air. When we are on the ocean we cango down by using our diving rudders, and in much quicker time than byfilling our tanks."
"How is that?" asked the seeker after the Pandora's gold.
"Filling the tanks is slow work in itself," replied Tom, "and they haveto be filled very carefully and evenly, so we don't stand on our sternor bow in going down. We want to sink on an even keel, and sometimesthis is hard to accomplish. But we are doing it now," and he calledattention to an indicator which told how much the M. N. 1 might belisting to one side or to one end or the other.
A submarine, as everyone knows, is essentially a water-tight tank,shaped like a cigar, with a propeller on one end. It can sink below thesurface and move along under water. It sinks because rudders force itdown, and water taken into tanks in its interior hold it to a certaindepth. It can rise by ejecting this extra water and by setting therudders in the proper position.
A submarine moves under water by means of electric motors, the currentof which is supplied by storage batteries. On the surface when thehatches can be opened, oil or gasolene engines are used. These enginescannot be used under water because they depend on a supply of air, oroxygen, and when the submarine is tightly sealed all the air possibleis needed for her crew to breathe. While cruising on the surface asubmarine recharges her storage batteries to give her motive power whenshe is submerged.
There are many types of submarines, some comparatively simple andsmall, and others large and complex. In some it is possible for thecrew to live many days without coming to the surface.
Tom Swift's reconstructed craft compared favorably with the best andlargest ever made, though she was not of exceptional size. She was verystrong, however, to allow her to go to a great depth, for the fartherdown one goes below the surface of the sea, the greater the pressureuntil, at, say, six miles, the greatest known depth of the ocean, thepressure is beyond belief. And yet is possible that marine monstersmay live in that pressure which would flatten out a block of solidsteel into a sheet as thin as paper.
"Well, we are as deep down as it is safe to go in the river," announcedTom, as the gauge showed a distance below the surface of a little lessthan twenty-nine feet. "Now we'll move into the bay. How do you likeit, Mr. Hardley?"
"Very well, so far. But it isn't very exciting yet."
"Bless my accident policy!" exclaimed Mr. Damon, "I hope you aren'tlooking for excitement."
"I'm used to it," was the answer. "The more there is the better I likeit."
"Well, you may get your wish," said Tom.
He turned a lever, and those on board the submarine became conscious ofa forward motion. She was no longer sinking.
She trembled and vibrated as the powerful electric motors turned herpropellers, and Tom, having seen that all was running smoothly in themain engine room, called Mr. Damon, Ned, and Mr. Hardley to him.
"We'll go into the forward pilot house and give Mr. Hardley a viewunder water," he announced. "Of course, you'll see nothing like whatyou'll view when we're in the ocean," added the young inventor, "but itmay interest you."
The four were soon in the forward compartment of the craft. She couldbe directed and steered from here when occasion arose, but now Tom wasletting his navigator direct the craft from the controls in the mainengine room. A conning tower, rising just above the deck of the craft,gave the pilot the necessary view.
"Here you are!" exclaimed Tom, as he switched out the lights in thecabin. For a moment they were in darkness, and then, with a click,steel plates, guarding heavy plate glass bull's-eyes, moved back, andMr. Hardley for the first time looked out on an underwater scene. Hesaw the murky waters of river down which they were proceeding to thebay moving past the glass windows. Now and then a fish swam up,looking in, and, with a swirl of its tail, shot away again, apparentlyfrightened well-nigh to death.
"Bless my shoe laces, Tom!" exclaimed Mr. Damon, "this isn't a markercompared to some of the sights we've seen, is it?"
"I can imagine not," said Mr. Hardley. "But it is interesting. I shallbe anticipating more wonderful sights."
"And you'll get them!" exclaimed Ned. "Do you remember, Tom, the timethe big octopus tried to hold us back?"
"Yes, indeed," answered the young inventor. "That gave us a scare forthe time being."
Steadily the M. N. 1 kept on her way under water. Her path wasilluminated to a considerable degree by a broad, diffused beam of lightfrom a powerful searchlight that was fixed just back of the conningtower, giving the helmsman a certain degree of vision. This light alsoserved to illuminate the water, so that those in the forward cabincould see what was going on around them.
"There isn't much of interest in the river," said Tom. "No big fish, oranything else of moment. Even in the bay we won't see much to attractour attention. But I want to make sure everything is working smoothlybefore we start for the West Indies."
"That's right!" agreed Mr. Hardley. "We want to make a success of thistrip."
He remained at the glass bull's-eyes, now and then exclaiming as someshad or other fair-sized fish came into view. Suddenly, however, hisexclamation was sharper than usual.
"Look!" he exclaimed. "There's part of a wreck!"
Ned, Mr. Damon, and Tom looked out and saw, sweeping past them, theribs and worm-eaten timbers of some craft, lying on the bottom of theriver.
"Yes, that's the remains of an old brick scow," the young inventorexplained. "That's one of our water-marks, so to speak. It is at thebend of the river. We turn now, and head for the bay."
As he spoke they all became aware of a sudden swerve in the course ofthe submarine. The helmsman had, doubtless, noted the "water-mark," asTom termed it, and as an automobilist on land might swing at thecross-roads, the steersman was changing the course of his craft.
"We'll go deeper," said Tom a moment later, as the wreck passed out ofview. "We can go about fifty feet down now. Yes, he's sinking her," headded, as a gauge showed the craft to be descending. "Nelson knows hisbusiness all right."
"He is your captain?" asked Mr. Hardley.
"One of the best, yes. He'll go with us on the search for the Pandora."
They talked of various matters, Tom relating to Mr. Hardley how a tughad rammed the brick scow so
me years ago, and sunk it in the river.
The submarine was now about forty-eight feet below the surface, andsuddenly they all became aware that her speed had increased.
"Guess he's going to give the motors a good try-out," observed Tom. "Ithink I'll go back to the engine room. You may remain here, if youlike, and you'll probably see--"
A cry from Mr. Damon interrupted him.
"Bless my rubber boots, Tom! Look!" cried the eccentric man. "We'regoing to ram a mud bank!"
As he spoke they all became aware of a solid black mass looming infront of the bull's-eye window. An instant later the submarine came toa jarring stop, as if she had struck some soft, yielding substance.There was a confused shouting throughout the craft, the noise ofmachinery, a trembling and vibration, and then ominous quiet.
Tom Swift and His Undersea Search; Or, the Treasure on the Floor of the Atlantic Page 8