'Purest and most delightful of all streams glides along the _Aqua Virgo_, so named because no defilement ever stains it. For while all the others, after heavy rain show some contaminating mixture of earth, this alone by its ever pure stream would cheat us into believing that the sky was always blue above us. Ah! how express these things in words worthy of them? The _Aqua Claudia_ is led along on the top of such a lofty pile that, when it reaches Mount Aventine, it falls from above upon that lofty summit as if it were watering some lowly valley. It is true that the Egyptian Nile, rising at certain seasons, brings its flood of waters over the land under a cloudless sky; but how much fairer a sight is it to see the Roman Claudia flowing with a never-failing stream over all those thirsty mountain tops, and bringing purest water through a multitude of pipes to so many baths and houses. When Nile retreats he leaves mud behind him; when he comes unexpectedly he brings a deluge. Shall we not then boldly say that our Aqueducts surpass the famous Nile, which is so often a terror to the dwellers on his banks either by what he brings or by what he leaves behind him? It is in no spirit of pride that we enumerate these particulars, but in order that you may consider how great diligence should be shown by you to whom such splendid works are entrusted. 'Wherefore, after careful consideration, we entrust you for this Indiction with the _Comitiva Formarum_, that you may zealously strive to accomplish what the maintenance of such noble structures requires. Especially as to the hurtful trees which are the ruin of buildings, [inserting their roots between the stones and] demolishing them with the destructiveness of a battering-ram: we wish them to be pulled up by the roots, since it is no use dealing with an evil of this kind except in its origin. If any part is falling into decay through age, let it be repaired at once: the first expense is the least. The strengthening of the Aqueducts will constitute your best claim on our favour, and will be the surest means of establishing your own fortune. Act with skill and honesty, and let there be no corrupt practices in reference to the distribution of the water.' 7. FORMULA OF THE PRAEFECT OF THE WATCH OF THE CITY OF ROME. [Sidenote: Praefectus Vigilum Urbis Romae.]