Cowley was the fourth son (and one of seventeen children) of a customs house agent and his wife from Sydenham in South London.
[1] Cowley worked with Alfred Neubauer, sub-librarian at the Bodleian Library, from 1890 onwards on the Samaritan liturgy; the results were published in two volumes in 1909.
[1] He returned to Oxford as Bodley's Librarian, succeeding Falconer Madan, in 1919 (the year in which he was appointed as a Fellow of the British Academy).
Space for acquisitions was a perennial problem; coins and engraved portraits were transferred to the Ashmolean Museum, and Cowley's preferred option of an extension to the Bodleian opposite its main site was eventually accepted just before he retired.
[1] In 1923 he published The Aramaic Papyri of the Fifth Century, a revision of his 1906 work, incorporating the critical results of the best-known Semitic scholars, his original text largely unaltered.