Æth"o*gen (&?;), n. [Gr. &?; fire, light + -gen.] (Chem.) A compound of nitrogen and boro&?;, which, when heated before the blowpipe, gives a brilliant phosphorescent; boric nitride.
Æ"thri*o*scope (&?;), n. [Gr. &?; clear + &?; to observe.] An instrument consisting in part of a differential thermometer. It is used for measuring changes of temperature produced by different conditions of the sky, as when clear or clouded.
Æ`ti*o*log"ic*al (&?;), a. Pertaining to ætiology; assigning a cause. -- Æ`ti*o*log"ic*al*ly, adv.
Æ`ti*ol"o*gy (&?;), n. [L. aetologia, Gr. &?;; &?; cause + &?; description: cf. F. étiologie.] 1. The science, doctrine, or demonstration of causes; esp., the investigation of the causes of any disease; the science of the origin and development of things.