He was admitted to the bar and practised law for a short time in his native city, where he became a judge of the civil court.

His literary and his historical tastes induced him to abandon his profession and devote himself to the history of the Catholic Church in its first four centuries.

In 1874 he translated James Spencer Northcote and W. R. Brownlow's Roma Sotterranea, making many additions and annotations to it.

An intimate acquaintance with Giovanni Battista de Rossi and his own studies along various lines, led him to undertake a history of the persecutions suffered by the Christians at the hand of the Roman authorities.

According to Allard, their treatment of the Christians arose from no reasons of statesmanship or adherence to traditional policy, but was based entirely on low and unworthy motives.