This translation of what may, perhaps, be called the most popular of all Boudon's works, was undertaken with the desire of furthering the holy object for which it was written, in the way which the venerable author specially recommended; for one of the means, and, indeed, one of the chief means, which he prescribes for spreading devotion to the Holy Angels, is the distribution of well selected books on the subject." This means," he writes, "includes almost all the others, since it both gives them honor and teaches it."It is superfluous to add that the doctrines it contains are not the offspring of the writer's imagination, or his mere private opinions, but that they rest on the solid basis of Catholic theology, and are in faithful accordance with the teaching of the Church.