Inventors in England sent
improved deep-sea thermometers to the Challenger for testing. They'd
developed the new reversing thermometer to solve the problem Challenger
scientists faced: how to measure the water temperature at a determined
depth, without assuming that the coldest water was necessarily at
the ocean bottom.
The Challenger scientists lowered the new reversing thermometer
to the chosen depth. Then, by pulling up on the attched rope to
release a catch, they flipped the thermometer upside-down and recorded
the temperature at that specific depth.