This work comes in three parts. The first part is devoted to the prayers of the Mass. At the end of this section is a striking miracle of the Holy Eucharist. The second part is devoted to the ceremonies of the Holy Sacrifice of the Mass, according to the Tridentine Rite. This is very useful for any priest who wishes to devoutly celebrate the Mass. This even includes instructions for when a priest should put his spectacles (glasses) on to read from the Missal and when to remove them. The last section contains prayers of preparation for Mass and in thanksgiving after Mass. In the preface we read: "These different writings give evidence of the zeal that animated our venerated author in regard to the divine Sacrifice on our altars. From his childhood he was admired for the tender devotion with which he attended Mass, received Communion, or spent his time in adoring the messed Sacrament. This virtue only grew and became more perfect as he advanced in age. Even in the midst of the world, notwithstanding the occupations and the cares of the profession which he at first embraced, he went every day to visit his dear Lord exposed in one of the churches of Naples, and there on his knees and immovable, he spent long hours before the altar, contemplating the object of his affection with so humble and so recollected an attitude, that he appeared to be out of himself; all persons that saw him were profoundly edified. Such piety was to receive its reward; for thus we read in his writings: .. I feel myself bound, at least out of gratitude to my Jesus in the Holy Sacrament, to declare that by means of this devotion of visiting the Most Blessed Sacrament, which I practised, though with so much tepidity and in so imperfect a manner, I abandoned the world, in which, unfortunately. I lived until six. and-twenty years of age."" Saint Alphonsus makes an interesting prophesy: "And this offering which our Lord then made of himself did not limit itself to that moment, but it only then began; it always has continued since, and it will continue forever. It is true it will cease on earth at the time of Antichrist: the Sacrifice of the Mass is to be suspended for twelve hundred and ninety days; that is, for three years six months and a half, according to the prophecy of Daniel: And from the time when the continual sacrifice shall be taken away, and the abomination unto desolation shall be set up, there shall be a thousand two hundred ninety days.' Yet the Sacrifice of Jesus Christ will never cease, since the Son of God will always continue to offer himself to his Father by an eternal sacrifice, for he himself is the priest and the victim, but ao eternal victim and an eternal priest, not according to the order of Aaron."