Epistle XVIII. To Agnellus, Bishop of Terracina. Gregory to Agnellus, &c. It has come to our ears—a thing shocking to be told—that some in your parts worship trees, and perpetrate many other unlawful things contrary to the Christian faith.  And we wonder why your Fraternity has delayed correcting this by strict punishment.  On this account we exhort you by this present writing to cause these persons to be sought out by diligent enquiry, and such vengeance to be executed on them that both God may be pacified and their punishment may be an example of rebuke to others. We have written also to Maurus the Viscount that he should afford aid to your Fraternity in this matter, that so you may be unable to find any excuse for not apprehending them.  Further, as we find that many excuse themselves from keeping watch over the walls, let your Fraternity be careful to suffer no man, either under the name of our or your Church, or under any other pretext, to be exempted from keeping watch:  but let all generally be compelled, to the end that, while all keep watch, the custody of the city may, by the help of the Lord , be the better provided for.