In the translator's preface, Hill writes:
"As far as I can ascertain, the De Trinitate has been translated completely into English three times in the last century: Library of the Nicene Fathers in 1887; The Works of Aurelius Augustine (a series begun in 1872) in 1934; and in The Fathers of the Church (a USA series) in 1963." (p.60)By my count, there was a translation done by Arthur West Haddan in 1872 that was published as vol. 7 of the Marcus Dods series of Augustine's works in 1878. The Haddan translation was further edited by William G.T. Shedd for the Schaff series in 1887. There was also a translation done by Stephen McKenna for vol. 45 of the CUA Fathers of the Church series, in 1963 (a revised selection from this translation was also used for the Cambridge Texts in the History of Philosophy series in 2002). Haddan is the only previous English translation that McKenna lists in his selected bibliography.
Am I missing something here, or is Hill's count simply off? We have an 1887 translation (Haddan-Shedd). We have a 1963 translation (McKenna). The 1934 translation is a mystery to me... even if Hill is referring to the two different publications of Haddan as separate translations, the date seems to be wrong. The Dods series did begin in 1872, but I think that it ended in 1934, and with a republication of vol.1-2 (The City of God) rather than with On the Trinity.
Hill doesn't provide any bibliographical information for this, so there's not really much to go on. Does anyone know of a 1934 translation of Augustine's de Trinitate that I'm failing to notice? Or is Hill simply mistaken? My suspicion is that he's counting Shedd as one and Haddan as another, and there's some issue with the date of the Haddan translation he has in mind. But I wouldn't want to overlook something if there's a mysteriously low-profile translation out there.