John C. Swallow
|John Crossley Swallow|
|Born||October 11, 1923|
|Died||December 3, 1994(aged 71)|
John Crossley Swallow FRS (1923–1994) was an English oceanographer who invented the Swallow float or sometimes referred to as a neutral buoyance float, a scientific drifting bottle created based on the method used by shipwrecked sailors who placed and sealed messages in bottles and hope that the said bottles will reach any inhabited shores so that people can help them.
He was elected a Fellow of the Royal Society in 1968. He candidature citation read: "Dr. J.C. Swallow is internationally known both for his distinguished geophysical work on the voyages of H.M.S. "Challenger", and for his measurements of deep ocean currents. He is the inventor of the "Swallow float", a hydrostatically stable, freely drifting source of sound underwater, which can be followed by a ship at the surface. By numerous observations with this ingenious device, he and others have completely changed our picture of the deep circulation of the ocean, showing the presence of strong deep currents in the western North Atlantic, and a reverse flow beneath the Gulf Stream. He has recently contributed to our knowledge of the equatorial undercurrent and of other currents in the Indian Ocean. Dr. Swallow combines a devotion to his work and a careful attention to detail with a mastery of the practical handling of a research ship at sea. The quality and originality of his contributions has already been recognized in the U.S.A. by the award of the Bigelow Medal and of the Albatross Award of the American Miscellaneous Society." 
Swallow's float was invented so that it would go underwater but keep afloat at a particular depth. The people on board the ship that follows the bottle should be able to know its location at all times. The Swallow float was also created with the ability to make sound signals into the water. Such sound signals would be heard and located by scientists aboard the ship, including the location of the bottle itself. Because of this apparatus, scientists were able to learn how water flows in the deep ocean. Many surface currents, the Gulf Stream for example, have countercurrents or currents that flow under the surface currents. Countercurrents flow by going to the opposite direction but within the same path flow of the surface current. Because of Swallow's float, scientists were also able learn to that there is no steady water circulation within the deep ocean; this is because, sometimes, the water keeps going round and round in a huge whirling action – creating an eddy – which drifts along slowly.
- Charnock, H. (1997). "John Crossley Swallow. 11 October 1923--3 December 1994: Elected ER.S 1968". Biographical Memoirs of Fellows of the Royal Society 43: 505. doi:10.1098/rsbm.1997.0028.
- "John C. Swallow, Measuring Ocean Currents, Movement of Ocean Water, Oceanography". The New Book of Knowledge, Grolier Incorporated. 1977., pages 33 [letter O] and 568 [letter S].
- "Library and Archive catalogue". Royal Society. Retrieved 2012-03-02.