The entrance into Mayence, at one o'clock at night, was quite _impressive_. On the opposite side of the river, in Cassel, is an extensive military establishment, through the gates and court of which we had to pass. The postillion sounded a martial air on his trumpet, and the sentinel, opening the ponderous gates, admitted us to the bridge of boats on which we crossed the Rhine to the city. Every thing was still and quiet, but our rumbling diligence; the stars and the lights of the town were looking at their portraits in the river. At the city portals, another blast of the trumpet[10] procured us admission, but no living thing was to be seen, except the military 'guardians of the night.' To-day it rains torrents. So I will merely tell you, in guide-book style, that Mayence, as well as Cologne, owes its origin to the Romans, and was occasionally the residence of some of the emperors. The city has also been an electorate of the German empire, but at present it belongs to Prussia; and it is remarkable, that with a population of thirty-two thousand, it has a garrison of twelve thousand soldiers. It claims the honor of being the birth-place of Guttenberg, one, at least, of the inventors of printing, of whom there is a statue in one of the squares. I have been to see the cathedral, noted only for antiquity, and for the numerous monuments and statues of church dignitaries in the interior. * * * * * COBLENTZ, (ON THE RHINE,) SEPTEMBER.--The steam-boat left the quay at Mayence this morning at six, with about one hundred passengers, mostly English, on their homeward retreat. For two or three miles, the banks of the river continued to be low and tame. We passed the palace of the Grand Duke of Nassau, a fine edifice, near the river The classical Brunnens of Langen-Schwalbach are a few miles in the interior.