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Time article October 12, 1953.
Her name was the Trieste, after the troubled city whose funds helped build her, Trieste Bathyscapheand she was about the strangest craft to sail the Tyrrhenian Sea since the time of Ulysses. Her skipper was an adventurer of 60 (Ulysses would have liked that), and her destination was one that Ulysses would have envied. The Trieste headed last week for the bottom of the sea, into the dark Tyrrhenian Trench to the west of southern Italy, where no ship steered by living men had ever gone before.
The Trieste is Professor Auguste Piccard's newest "bathyscaphe”. On the surface she looks vaguely like a ship, but she is really an underwater balloon designed to sail the depths of the sea just as a blimp navigates the air. Her crew compartment is a forged and welded steel sphere about 8 ft. in diameter with walls 3.5 in. thick. This is the only part designed to resist the enormous pressure of the deep sea. It hangs below a "floater": a submarine-shaped hull of thin steel about 6o feet long and filled with 22,000 gallons of gasoline.
The floater does the duty of a balloon's gas-filled bag. Since its gasoline is about two-thirds as heavy as sea water and only slightly compressible, its buoyancy supports the ship even under heavy pressure.
Electromagnetic Ballast. The Trieste's vertical movements are controlled just like a balloon's. To descend, it releases gasoline, which makes it heavier in the water. To rise it drops ballast. The Trieste's ballast is four tons of iron filings stowed in containers in the floater. Electromagnets, which make iron filings stick together, keep the ballast from moving. When their current is cut off, the filings flow into the sea. This system "fails safe." If anything happens to the ship's power supply, the ballast is dropped automatically. Then the Trieste, lightened, will rise to the surface.
The floater has two small, electrically driven propellers, which move it horizontally. They make the Trieste more like a blimp than like the passively floating balloon in which Professor Piccard, then a mere 48, set an altitude record of 53,-152.8 ft. in 1932.
10,000 Feet Down. On a rough and rainy night last week, this odd craft was towed to a point i8 miles south of the island of Ponza where the Tyrrhenian Trench is 10,000 ft. deep. Just after the cheerless dawn, old Professor Piccard, a black Basque beret over his white hair, boarded the Trieste from an Italian navy corvette and climbed down a tube leading to the pressure sphere. His son, Jacques, 30, was already on board, crammed among oxygen bottles, apparatus and 102 instruments, including a movie camera. When the professor closed a massive door, the Trieste was ready to dive. Men from the corvette opened valves, letting sea water into parts of the floater. They scurried aboard their boats, and the Trieste sank gently under the gray sea.
Trieste Bathyscaphe Diagram
Two hours and 18 minutes later she popped to the surface, cheerful as a bubble. After the water had been forced from the access tube, Professor Piccard and Jacques came to the deck of the floater and were rowed to the corvette. Leaning on his son, the professor whispered in French: "You speak, Jacques. The credit is all yours."
Soft Wadding, Jacques smiled and refused. For a moment father and son clung to each other, as if too moved to speak. Then the old professor began: "It was very important, very lovely. And I must say that the chief merit of this undertaking goes to my son Jacques. It was he who guided the Trieste." There had been no trouble at all; the Trieste had functioned perfectly. She had snuggled down on the sea bottom (where the pressure was about 500 pounds per square inch). .....
he plans to take the Trieste to the east coast of the U.S. where the ocean is much deeper than the Tyrrhenian Trench.

On January 23, 1960, Trieste reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying Jacques Piccard (son of Auguste) and Lieutenant Don Walsh, USN. This was the first time a vessel, manned or unmanned, had reached the deepest point of the Earth's oceans. The onboard systems indicated a depth of 11,521 metres (37,799 ft), although this was revised later to 10,916 metres (35,814 ft) and more accurate measurements made during 1995 have found the Challenger Deep to be slightly shallower, at 10,911 metres (35,797 ft). No vessel has ever reached this depth before or since.

Beginning April 1963, Trieste was modified and used in the Atlantic Ocean to search for the missing submarine USS Thresher (SSN-593). During August 1963, Trieste found the wreck off the coast of New England, 8,400 feet (2.56 km) below the surface.[6] Trieste was changed, improved and redesigned so many times that almost no original parts remain. The Trieste was transported to the Washington Navy Yard where it was exhibited along with the Krupp pressure sphere in the National Museum of the U.S. Navy at the Washington Navy Yard during 1980. Her original Terni pressure sphere was incorporated into the Trieste II.