instrument for ascertaining the purity of the atmospherical air, or the quantity of pure oxygen or vital air contained in it, chiefly by means of its diminution, or the abstraction of it by exposing certain substances to its action. Several kinds of these have been invented. See Chemistry Index.

Eudokia, (Athenia, before her conversion to Christianity), a celebrated lady, the daughter of Leonius, a philosopher of Athens; who gave her such a learned education, that at his death, he left her only a small legacy, saying she was capable to make her own fortune: but pleading at Athens without success against her two brothers, for a share in her father's estate, she carried her cause personally by appeal to Constantinople; recommended herself to Pulcheria, the sister of the emperor Theodolius the younger; embraced Christianity, was baptized by the name of Eudokia, and soon after married to the emperor. Their union lasted a considerable time: but a difference at last taking place, on account of the emperor's jealousy, excited by Chrysapius the eunuch, she retired to Jerusalem, where she spent many years in building and adorning churches and in relieving the poor. Dupin says, that she did not return thence till after the emperor's death: but Cave tells us, that she was reconciled to him, returned to Constantinople, and continued with him till his death; after which she went again to Palestine, where she spent the remainder of her life in pious works. She died in the year 450, according to Dupin; or 459, according to Cave: the latter observes, that on her deathbed she took a solemn oath, by which she declared herself entirely free from any stains of un-Eudoxians chastity. She was the author of a paraphrase on the eight first books of the Old Testament in heroic verse; and of a great number of poems, which are lost.