The Baillie sounding machine was one of various sinkers used to pull the Challenger's sounding line to the ocean bottom. Like the sinker with a sampling cup, the Baille also brought back a sample from the bottom. This sinker was a hollow tube threaded through donut-shaped weights. These weights drove the hollow tube down into the seafloor and then a release catch dropped them. As the tube was pulled up, a butterfly valve swung shut and held the sample inside. The core of trapped mud or sediment was about 5 cm 92 inches) across and as much as one meter (3 feet) in length.
The Challenger crew took 360 soundings throughout the world's oceans. This tremendous effort was still only 360 pinpoints of known depth for all the 350 million square kilometers (140 million square miles) of the world's seafloor. But added to data from earlier expeditions, these soundings helped outline many major undersea mountain ranges, deep trenches and wide flat plains on the ocean floor.
This sounding line sinker had a small cup that sunk into the seafloor and brought up a sample of sediments or mud.