Chapter Four

Tom is Imprisoned



"Well, I must say he's a cool one," remarked Tom, as the

echoes of Mr. Berg's steps died away. "The idea of thinking

his boat better than ours! I don't like that man, dad. I'm

suspicious of him. Do you think he came here to steal some

of our ideas?"



"No, I hardly believe so, my son. But how did you discover

him?"



"Just as you saw, dad. I heard a noise and went back there

to investigate. I found him sneaking around, looking at the

electric propeller plates. I went to grab him just as he

stumbled over a hoard. At first I thought it was one of the

old gang. I'm almost sure he was trying to discover

something."



"No, Tom. the firm he works for are good business men, and

they would not countenance anything like that. They are

heartless competitors, however, and if they saw a legitimate

chance to get ahead of me and take advantage, they would do

it. But they would not sneak in to steal my ideas. I feel

sure of that. Besides, they have a certain type of submarine

which they think is the best ever invented, and they would

hardly change at this late day. They feel sure of winning

the Government prize, and I'm just as glad we're not going

to have a contest."



"Do you think our boat is better than theirs?"



"Much better, in many respects."



"I don't like that man Berg, though," went on Tom.



"Nor do I," added his father. "There is something strange

about him. He was very anxious that I should compete.

Probably he thought his firm's boat would go so far ahead of

ours that they would get an extra bonus. But I'm glad he

didn't see our new method of propulsion. That is the

principal improvement in the Advance over other types of

submarines. Well, another week and we will be ready for the

test."



"Have you known Mr. Berg long, dad?"



"Not very. I met him in Washington when I was in the

patent office. He was taking out papers on a submarine for

his firm at the same time I got mine for the Advance. It is

rather curious that he should come all the way here from

Philadelphia. merely to see if I was going to compete. There

is something strange about it, something that I can't

understand."



The time was to come when Mr. Swift and his son were to

get at the bottom of Mr. Berg's reasons, and they learned to

their sorrow that he had penetrated some of their secrets.



Before going to bed that night Tom and Mr. Sharp paid a

visit to the shed where the submarine was resting on the

ways, ready for launching. They found Mr. Jackson on guard

and the engineer said that no one had been around. Nor was

anything found disturbed.



"It certainly is a great machine," remarked the lad as he

looked up at the cigar-shaped bulk towering over his head.

"Dad has outdone himself this trip."



"It looks all right," commented Mr. Sharp. "Whether it

will work is another question."



"Yes, we can't tell until it's in the water," con ceded

Tom. "But I hope it does. Dad has spent much time and money

on it."



The Advance was, as her name indicated, much in advance of

previous submarines. There was not so much difference in

outward construction as there was in the means of propulsion

and in the manner in which the interior and the machinery

were arranged.



The submarine planned by Mr. Swift and Tom jointly, and

constructed by them, with the aid of Mr. Sharp and Mr.

Jackson, was shaped like a Cigar, over one hundred feet long

and twenty feet in diameter at the thickest part. It was

divided into many compartments, all water-tight, so that if

one or even three were flooded the ship would still be

useable.



Buoyancy was provided for by having several tanks for the

introduction of compressed air, and there was an emergency

arrangement so that a collapsible aluminum container could

be distended and filled with a powerful gas. This was to be

used if, by any means, the ship was disabled on the bottom

of the ocean. The container could be expanded and filled,

and would send the Advance to the surface.



Another peculiar feature was that the engine-room, dynamos

and other apparatus were all contained amidships. This gave

stability to the craft, and also enabled the same engine to

operate both shafts and propellers, as well as both the

negative forward electrical plates, and the positive rear

ones.



These plates were a new idea in submarine construction,

and were the outcome of an idea of Mr. Swift, with some

suggestions from his son.



The aged inventor did not want to depend on the usual

screw propellers for his craft, nor did he want to use a jet

of compressed air, shooting out from a rear tube, nor yet a

jet of water, by means of which the creature called the

squid shoots himself along. Mr. Swift planned to send the

Advance along under water by means of electricity.



Certain peculiar plates were built at the forward and aft

blunt noses of the submarine. Into the forward plate a

negative charge of electricity was sent, and into the one at

the rear a positive charge, just as one end of a horseshoe

magnet is positive and will repel the north end of a compass

needle, while the other pole of a magnet is negative and

will attract it. In electricity like repels like, while

negative and positive have a mutual attraction for each

other.



Mr. Swift figured out that if he could send a powerful

current of negative electricity into the forward plate it

would pull the boat along, for water is a good conductor of

electricity, while if a positive charge was sent into the

rear plate it would serve to push the submarine along, and

he would thus get a pulling and pushing motion, just as a

forward and aft propeller works on some ferry boats.



But the inventor did not depend on these plates alone.

There were auxiliary forward and aft propellers of the

regular type, so that if the electrical plates did not work,

or got out of order, the screws would serve to send the

Advance along.



There was much machinery in the submarine There were

gasolene motors, since space was too cramped to allow the

carrying of coal for boilers. There were dynamos, motors and

powerful pumps. Some of these were for air, and some for

water. To sink the submarine below the surface large tanks

were filled with water. To insure a more sudden descent,

deflecting rudders were also used, similar to those on an

airship. There were also special air pumps, and one for the

powerful gas, which was manufactured on board.



Forward from the engine-room was a cabin, where meals

could be served, and where the travelers could remain in the

daytime. There was also a small cooking galley, or kitchen,

there. Back of the engine-room were the sleeping quarters

and the storerooms. The submarine was steered from the

forward compartment, and here were also levers, wheels and

valves that controlled all the machinery, while a number of

dials showed in which direction they were going, how deep

they were, and at what speed they were moving, as well as

what the ocean pressure was.



On top, forward, was a small conning, or observation

tower, with auxiliary and steering and controlling apparatus

there. This was to be used when the ship was moving along

on the surface of the ocean, or merely with the deck awash.

There was a small flat deck surrounding the conning tower

and this was available when the craft was on the surface.



There was provision made for leaving the ship when it was

on the bed of the ocean. When it was desired to do this the

occupants put on diving suits, which were provided with

portable oxygen tanks. Then they entered a chamber into

which water was admitted until it was equal in pressure to

that outside. Then a steel door was opened, and they could

step out. To re-enter the ship the operation was reversed.

This was not a new feature. In fact, many submarines to-day

use it



At certain places there were thick bull's-eye windows, by

means of which the under-water travelers could look out into

the ocean through which they were moving. As a defense

against the attacks of submarine monsters there was a steel,

pointed ram, like a big harpoon. There were also a bow and a

stern electrical gun, of which more will be told later.



In addition to ample sleeping accommodations. there were

many conveniences aboard the Advance. Plenty of fresh water

could be carried, and there was an apparatus for distilling

more from the sea water that surrounded the travelers.

Compressed air was carried in large tanks, and oxygen could

be made as needed. In short, nothing that could add to the

comfort or safety of the travelers had been omitted. There

was a powerful crane and windlass, which had been installed

when Mr. Swift thought his boat might be bought by the

Government. This was to be used for raising wrecks or

recovering objects from the bottom of the ocean. Ample

stores and provisions were to be carried and, once the

travelers were shut up in the Advance, they could exist for

a month below the surface, providing no accident occurred.



All these things Tom and Mr. Sharp thought of as they

looked over the ship before turning in for the night. The

craft was made immensely strong to withstand powerful

pressure at the bottom of the ocean. The submarine could

penetrate to a depth of about three miles. Below that it was

dangerous to go, as the awful force would crush the plates,

powerful as they were.



"Well, we'll rush things to-morrow and the next day,"

observed Tom as he prepared to leave the building. "Then

we'll soon see if it works."



For the next week there were busy times in the shop near

the ocean. Great secrecy was maintained, and though

curiosity seekers did stroll along now and then, they

received little satisfaction. At first Mr. Swift thought

that the visit of Mr. Berg would have unpleasant results,

for he feared that the agent would talk about the craft, of

which he had so unexpectedly gotten a sight. But nothing

seemed to follow from his chance inspection, and it was

forgotten.



It was one evening, about a week later, that Tom was alone

in the shop. The two mechanics that had been hired to help

out in the rush had been let go, and the ship needed but a

few adjustments to make it ready for the sea.



"I think I'll just take another look at the water tank

valves," said Tom to himself as he prepared to enter the big

compartments which received the water ballast. "I want to be

sure they work properly and quickly. We've got to depend on

them to make us sink when we want to, and, what's more

important, to rise to the surface in a hurry. I've got time

enough to look them over before dad and Mr. Sharp get back."



Tom entered the starboard tank by means of an emergency

sliding door between the big compartments and the main part

of the ship. This was closed by a worm and screw gear, and

once the ship was in the water would seldom be used.



The young inventor proceeded with his task, carefully

inspecting the valves by the light of a lantern he carried.

The apparatus seemed to be all right, and Tom was about to

leave when a peculiar noise attracted his attention. It was

the sound of metal scraping on metal, and the lad's quick

and well-trained ear told him it was somewhere about the

ship.



He turned to leave the tank, but as he wheeled around his

light flashed on a solid wall of steel back of him. The

emergency outlet had been closed! He was a prisoner in the

water compartment, and he knew, from past experience, that

shout as he would, his voice could not be heard ten feet

away. His father and Mr. Sharp, as he was aware, had gone to

a nearby city for some tools, and Mr. Jackson, the engineer,

was temporarily away. Mrs. Baggert, in the house, could not

hear his cries.



"I'm locked in!" cried Tom aloud. "The worm gear must have

shut of itself. But I don't see how that could be. I've got

to get out mighty soon, though, or I'll smother. This tank

is airtight, and it won't take me long to breath up all the

oxygen there is here. I must get that slide open."



He sought to grasp the steel plate that closed the

emergency opening. His fingers slipped over the smooth,

polished surface. He was hermetically sealed up--a captive!

Blankly he set his lantern down and leaned hopelessly

against the wall of the tank.



"I've got to get out," he murmured.



As if in answer to him he heard a voice on the outside,

crying:



"There, Tom Swift! I guess I've gotten even with you now!

Maybe next time you won't take a reward away from me, and

lick me into the bargain. I've got you shut up good and

tight, and you'll stay there until I get ready to let you

out."



"Andy Foger!" gasped Tom. "Andy Foger sneaked in here and

turned the gear. But how did he get to this part of the

coast? Andy Foger, you let me out!" shouted the young

inventor; and as Andy's mocking laugh came to him faintly

through the steel sides of the submarine, the imprisoned lad

beat desperately with his hands on the smooth sides of the

tank, vainly wondering how his enemy had discovered him.

****

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