THE MUD BANK
"WHAT'S that noise?" asked Mr.Hardley.
Mr.Hardley, Tom Swift, Mr.Damon, Ned Newton, Koku, and one or two navigating officers of the craft, were gathered in the operating cabin of the M.N.1.
"That's water being pumped into the tanks," explained Tom."We are now going down.If you'll watch the depth gauge you can note our progress.""Going down, are we?" remarked Mr.Hardley."Well, it's interesting to say the least," and he observed the gauge, which showed them to be twenty feet under the surface.
"Bless my hydrometer, but he's got nerve for a first trip in a submarine! 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 enough to give his visitor credit for what was due him.And indeed many a person is nervous going down in a submarine for the first time."Still we can't go more than thirty feet down in this water," went on Tom."A better test will be when we get about five hundred feet below the surface.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 under water, unless he watches the gauge.""Well, I think you'll find Mr.Hardley all right," said Mr.Damon, who seemed to have taken a strong liking to his new friend.
Certainly the latter showed no signs of nervousness as the craft slowly settled to the proper depth.He asked numberless questions, showing his interest in the operation of the M.N.1, but he showed not the least sign 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 our ballast tanks with water.We can rise, when needful, by forcing out this water by means of compressed air.When we are on the ocean we can go down byusing our diving rudders, and in much quicker time than by filling 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 have to be filled very carefully and evenly, so we don't stand on our stern or bow in going down.We want to sink on an even keel, and sometimes this is hard to accomplish.But we are doing it now," and he called attention to an indicator which told how much the M.N.1 might be listing 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 the surface and move along under water.It sinks because rudders force it down, and water taken into tanks in its interior hold it to a certain depth.It can rise by ejecting this extra water and by setting the rudders in the proper position.
A submarine moves under water by means of electric motors, the current of which is supplied by storage batteries.On the surface when the hatches can be opened, oil or gasolene engines are used.These engines cannot be used under water because they depend on a supply of air, or oxygen, and when the submarine is tightly sealed all the air possible is needed for her crew to breathe.While cruising on the surface a submarine recharges her storage batteries to give her motive power when she is submerged.
There are many types of submarines, some comparatively simple and small, and others large and complex.In some it is possible for the crew to live many days without coming to the surface.
Tom Swift's reconstructed craft compared favorably with the best and largest ever made, though she was not of exceptional size.She was very strong, however, to allow her to go to a great depth, for the farther down one goes below the surface of the sea, the greater the pressure until, at, say, six miles, the greatest known depth of the ocean, the pressure is beyond belief.And yet is possible that marine monsters may live in that pressure which would flatten out a block of solid steel 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 less than twenty-nine feet."Now we'll move into the bay.How do you like it, Mr.Hardley?""Very well, so far.But it isn't very exciting yet.""Bless my accident policy!" exclaimed Mr.Damon, "I hope you aren't looking for excitement.""I'm used to it," was the answer."The more there is the better I like it." "Well, you may get your wish," said Tom.
