Oilbird, common name for an owllike, cave-dwelling bird, Steatornis caripensis, belonging to the family Steatornithidae. It spends its days in dark caves, maneuvering by means of a batlike son...

Hydrophone, device that receives underwater sound waves and converts them to electrical energy; the voltage generated can then be read on a meter or played through a loudspeaker. The hydrophon...

Edgerton, Harold, 1903–90, American inventor and educator, b. Fremont, Nebr. He was educated at the Univ. of Nebraska and the Massachusetts Institute of Technology (D.Sc., 1931), and taught at...

McMillan, Edwin Mattison, 1907–91, American physicist, b. Redondo Beach, Calif., grad. California Institute of Technology, 1928, Ph.D. Princeton, 1932. On the faculty of the Univ. of Californi...

Echo sounder, an older instrumentation system for indirectly determining ocean floor depth. Echo sounding is based on the principle that water is an excellent medium for the transmission of so...

Echo, reflection of a sound wave back to its source in sufficient strength and with a sufficient time lag to be separately distinguished. If a sound wave returns within 1/10 sec, the human ear...

Goatsucker, common name for nocturnal or crepuscular birds of the order Caprimulgiformes, which includes the frogmouth, the oilbird, potoos, and nightjars. Goatsuckers are medium in size and a...

Submersible, small, mobile undersea research vessel capable of functioning in the ocean depths. Development of a great variety of submersibles during the later 1950s and 1960s came about as a ...

Pregnancy, period of time between fertilization of the ovum (conception) and birth, during which mammals carry their developing young in the uterus (see embryo). The duration of pregnancy in h...

Mine, in warfare, term formerly applied to a system of tunnels dug under an army fortification and ending in a chamber where either explosives were placed to be detonated at the chosen moment ...