careful consideration, and if the quoted material is sufficient in amount and in character to exert a pernicious influence, the work must be expurgated or placed upon the Index. Authors are cautioned against the wrongdoing of abusing each other whatever may be the difference of opinion, or of using harsh and condemnatory language against other writers whose works have not been condemned by the Church. These instructions and counsels are to be accepted as carrying the full Apostolic authority and as binding upon the Congregations, the examiners, and all others concerned.” Certain of the other Congregations, such as those on confession, on the rites of the Church, and on propaganda, assumed the right to prohibit books having to do with their particular subjects, but their prohibitions had to be confirmed by, and promulgated through, the Congregation of the Index. The _Magister_ of the palace had authority to issue in his own name prohibitions which were valid for the city of Rome. The individual edicts published by him in the name of the pope were of course general in their effect. From the time of Clement XI, 1700–1721, the prohibitions of individual works through bulls and briefs became much more frequent. After Benedict XIV, 1756, such prohibitions are to be found in allocations and in encyclicals. In 1664, Alexander VII ordered that the injunctions and penalties of Pius IV, as specified in the Index of Trent, should remain in force, but that all the other constitutions and decrees in regard to books, excepting only the _Bulla Coenae_, be revoked. In the introduction to the Index of 1758, Benedict XIV presents certain principles as controlling, from that time, the work of the censors. Books by heretics are to receive consideration only in the instances in which they treat of the Catholic faith, or teach heresies. The task of examining and supervising the entire literature of the world was at last recognised as one beyond the powers of the Church authorities. In 1869, a Bull of Pius IX restricts the penalty of the excommunication _latae sententiae_ to the reading, possession, etc., of books written by heretics, only when these not only contain heresies, but make a formal defence of the same, or when they have been specifically prohibited by title. In the case of a writer who had already been condemned for uttering heretical opinions, his later books were likely to be placed on the Index irrespective of the character of their contents. In 1615, for instance, the opinions of Copernicus were condemned by the Inquisition, and, a year later, his astronomical treatises were duly prohibited. The condemnation of a book by the Inquisition carried as a rule more weight than a prohibition by the Congregation. On the other hand, the Inquisition found difficulty in keeping up with its work.