A bathysphere, designed John H. J. Butler in 1928, is an un-powered deep-sea submersible that is lowered into the ocean on a cable. Watson Stillman Hydraulic Machinery Company handled the casting of the steel sphere. The first version was too heavy but they created a lighter design consisting of a hollow sphere of 1-inch-thick cast steel.
The vessel had quartz windows, the strongest transparent material of the time, and a 400-pound hatch that was bolted down before descent. Oxygen came from a high pressure cylinder inside the sphere. The vessel was suspended by a one-inch cable while a rubber hose carrying electrical supply and telephone wires allowed for communication with the occupants. Submerged the entire vessel weighed about 10,000 pounds.
Barton and William Beebe piloted the first manned dive of the bathysphere on June 6, 1930. They set a record of 3,028 feet that was unbroken for 15 years.
Beebe reported a world of astonishing creatures and a sea that sparkled like the night sky. Bellow his ship he said it “looked like the black pit-mouth of hell itself.”