Readestown, U. S. A., is a smart, flourishing little city upon a certain river which runs down to the sea, and it owes its founding and success to a family of wonderful inventors by the name of Reade. Frank Reade, Jr., the latest representative of the wonderful family, is a young man whose name is a household word the world over.

He is the inventor of so many wonderful machines, for traveling in the air, under water, or anywhere else that the people of this great country were by no means greatly surprised at the announcement which one day went forth that the young inventor had perfected a new submarine boat, and in conjunction with a famous scientist was about to make a trip of exploration through the great Atlantic valley, which is under the sea.

But they were interested if not surprised, and everybody was agog to know just when the expedition was to start. And all the people would await with great interest the outcome of the new and wonderful enterprise.

Some predicted a calamity. It did not seem an easy matter to remain under water in a submarine boat for days and weeks, living upon artificial air and deprived of heaven's light.

But those who knew Frank Reade, Jr., had no doubt of his success. Particularly Prof. Von Bulow, the distinguished German scientist, who was to accompany Frank. This gentleman was very enthusiastic over the enterprise.

He had dined with the young inventor in the cabin of the Dart, and had spent some hours in its trial under the surface of the river at Readestown. Therefore he was able to vouch for its efficiency and practicability.

"I will take my chances," he said, with a broad smile; "it will be no danger, I am very well assured." The professor was especially anxious to study phenomena of the deep sea, and also the topography of the Atlantic Valley.

All that was known of this mighty depression had been gained by deep sea soundings. Certain specimens of its bottom had been brought up by the lead. Various forms of animal life unknown to science had thus been discovered.

But it was only guess work after all. Here, however, was a mighty opportunity to explore the ocean depths literally. In his great machine shops at Readestown, Frank had constructed the Dart.

Every detail of its draughting and plans had been made by him in his secret model room. The machinists had done the work under his directions. In this manner the famous Dart was built. In shape it was not unlike the model of a pleasure yacht.

There was a hull of thinly rolled but strongest steel. It was provided with dead eye windows of convenient number, water-tight and provided with slides. Above the hull was an outer deck provided with a guard rail which extended from stem to stern.

Then above this deck was a cylindrical body with windows, of toughest plate glass, and doors in its ends. This was the cabin of the Dart, and it was divided into various compartments, which we will describe separately.

In the middle of the cabin cylinder was a section of straight plate glass, so that the travelers sitting in the cabin were in constant view of the sea and its depths. Two masts rose fore and aft, and forward was a pilot-house where were the nautical apparatus and the steering gear, as well as the electric keyboard.

For the propelling and lighting power of the Dart was furnished by electricity. Over the pilot-house was a most powerful electric searchlight. With this the bottom of the sea was made as plain as broad daylight, and was a mighty advantage.

This is a meager description of the exterior of the Dart. The interior was magnificent beyond description. Frank had spared no expense in the fittings of the Dart, so that it was a veritable floating palace.

The first cabin was richly furnished; the second cabin contained half a dozen fine staterooms. Beyond was the dining cabin, and then one came to the cook's galley.

Below decks, however, was the region of wonder and mystery. Here was all the wonderful and secret electrical machinery.

Also the mighty automatic reservoirs by which the Dart was made to sink or rise at the will of the inventor. Forward was the chemical room, where in tanks was stored the compressed air, and also manufactured the same, with which the travelers were enabled to live beneath the surface of the ocean.

Tubes went to every part of the cabin with this chemical product, and there was also an apparatus for consuming the vitiated air or gases. So that the air supply was always of the purest and best.

Truly, the submarine Dart was a wonderful product of the inventor's skill and ingenuity. Few, however, could appreciate it more fully than Prof. Von Bulow, who was fairly captivated with it. "It is a most wonderful thing," he declared earnestly. "There is nothing in the kaiser's land like it. You Americans are a wonderful people."

Frank was besieged with hundreds of applications for various purposes. Hosts of cranks applied for permission to accompany him. Some letters were beseeching, some threatening. One mildly insane woman wanted him to recover her son from the clutches of an octopus.

Another asked that her husband might be brought back from the realm of old Neptune. But one applicant, at least, received consideration at Frank's hands. He was a bearded sea captain, who told of the sinking of a pirate ship in a certain latitude with a vast treasure aboard.

Here was a reasonable request, and Frank agreed to look for it. He took the bearings as given him by Captain Bell and said: "If possible I will find your sunken treasure. It may be, though, that time and the action of the tides have buried it so deep that I will not be able to reclaim it."

"I think not, sir," said Captain Bell, eagerly. "It occurred, to be sure, forty years ago, but I think it is upon a reef not so very far beneath the surface." Then Captain Bell went on to tell the story of the lost treasure.

"I was quite a young man, then," he said, "and was in the navy, as captain of a small sloop-of-war, called the Utopia. "Reports were coming in thick and fast of Captain Longboots, the pirate, who was so venturesome as to penetrate within one hundred miles of New York City in quest of a prize.

"His ship, the Vestal Virgin, odd name for a pirate, was a fast sailer, and most of our war vessels could not keep in sight of her. "The pirate captain's real name nobody could learn, but he was called Captain Longboots from the immensely long boots which he wore at all times.

"But there was a suspicion in the navy department that he was really Isaac Van Dorn, once a captain in the service, and who had become disgruntled on account of a reprimand from a superior officer, and sought revenge upon the Government by starting out upon a tour of piracy.

"Well, the Secretary of the Navy selected me and the Utopia to go in chase of the pirate. "Just at this time there came a report that an English steamer had been overhauled, and a million dollars in American gold had been seized by Longboots.

"This settled the question. I was at once in receipt of sailing orders. "We left Annapolis one bright day, and sailing down the river, soon reached the open sea. "I had nothing to guide me but my nose. I followed it, however, for five hundred miles out to sea, and in the direction of Bermuda.

"My plan was not to attempt to overhaul the Vestal Virgin. "I caused the Utopia to be rigged up like a merchant vessel. The gunports were closed and painted, and everything warlike about her was concealed. "Then I lay in the track of foreign-going vessels for weeks. My game worked.

"It was some while before the pirate showed up; but she did eventually, and bore down upon us. "We made a show of running away, but she overhauled us like the wind. We did not have any trouble in letting her overtake us.

"She sent some hot shot across our bows and we hove to. We were all ready for a fight. "Behind our high bulwarks crouched our men all ready for boarding. The false ports could be knocked out in ten seconds, and an instant broadside given from ten guns. "Nearer drew the Vestal Virgin. When she was a hundred yards distant, Longboots himself appeared in the shrouds. I spoke to one of my men:

"'Pick that villain off; let it be a signal for the broadside.' "The order went along. Every man was ready. The gunner I had spoken to was a dead shot. "He fired, and Longboots dropped to the deck. Then open flew our ports and we sent solid shot into her hull.

"She went down instantly. We had just time to get away from the vortex. Only one of her men was saved. "He made a clean breast of all, and declared that there was fully a million and a half in treasure aboard the Vestal Virgin. We had some thoughts then of recovering it.

"But the soundings were too deep. No diver could live at that depth. We turned our course homeward. "And this is how it comes that the Vestal Virgin and her mighty treasure lies at the bottom of the sea." Frank had been deeply interested at this recital. As Captain Bell finished he said:

"I will make every endeavor, be sure, to recover that treasure. If I do, a fair share of it is yours." Captain Bell gripped Frank's hand. "I hope you will succeed," he said; "and I feel quite sure you will."

Then Frank showed the captain over the submarine boat. He was delighted. "Upon my word, skipper," he cried. "I'm an old sea dog and reckoned never to leave the surface of the ocean while in life. But I'd give a good deal to take this v'yage with you."

Frank was thoughtful a moment. He had taken a great liking to Captain Bell. "Do you mean that?" he asked. "With all my heart," replied the old skipper, eagerly. "And if I don't work and earn my passage you can put me off at the first port. Shall I go with you?"

"Yes," replied Frank; "you may."