Bathometer. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/Bathometer
An instrument that is used to measure water depth without the use of a sounding line. The bathometer does not require a line to extend to the bottom because it measures the difference in the gravitational effect of the water surface and of solid ground.
In deep water the closing mechanism is usually actuated by a screw propeller which begins to work when the line is being hauled in and can be set so as to close the waterbottle in a very few fathoms. A small but heavy water-bottle has been devised by Martin Knudsen, provided with a pressure gauge or bathometer, by which samples may be collected from any moderate depth down to about roc fathoms, on board a vessel going at full speed.