Another cool item from the Arctic Discoverer! When I found this 17” glass sphere on the ship in 2013, I thought it was a glass fishing float and bought it. I thought it was kinda big for a fishing float, so I did some research. They are actually made by Teledyne Benthos’. They are vacuum sealed instrument housings for deep sea exploring. This is what I found on the internet: “Flotation (Glass Spheres) Teledyne Benthos’ patented vacuum sealed glass floats and instrument housings are manufactured from precision-molded spheres to exact specifications. The edge of each hemisphere is ground flat to extreme tolerances. When used for flotation our hemispheres are matched, mated, and then evacuated to an absolute internal air pressure of less than 0.3 atmospheres. After evacuation, a sealant and protective tape are applied around the equator. Spheres sealed in this method are nearly impossible to open due to the force exerted upon them by the atmospheric pressure. In the case of the 43.2 cm (17 in) diameter float, this force is in excess of 880 kg (2000 lbs). (C-204-41) 2040-17V; Glass Flotation Sphere - 17”. Tested to a depth of 22,000 ft.” The glass is over ½” thick which explains why they weigh 39 pounds. These were used to help locate the wreck of the SS Central America. This sphere is still in excellent/new condition with no damage, cracks or chips.