to have twenty-five, two of which are of black porphyry. I found fourteen in the nave, not all alike. Most of the capitals are Ionic, but of different sizes, some pretty well executed, but much degraded; others originally bad; some are merely bossed out, and have never been finished: one is Corinthian, and one is Composite. There are said to be others built up in the wall, but they must be very small. About the altar, are two columns which seem to be chiefly of quartz, but with spots of hornblende, and two of a dark veined marble, but what is meant by black porphyry I do not know. Those of dark marble have Composite capitals, which Uggeri says are of serpentine, but I did not particularly observe them. The front exhibits a gallery of small columns, standing on a high unadorned wall. The contrast is _piquant_, but perhaps more so where the form is circular, as at the back of Santi Giovanni e Paolo. On descending the Aventine we have Monte Testaccio in full view. It is a hill 260 feet high, made of potsherds. The meadows in which it stands, are the property of the Roman people, and the scene of many of their festivities. One corner of them forms a burying-ground for heretics, just under the pyramid of Caius Cestius. Who it was that provided for himself such a conspicuous sepulchre, is not determined; but this work of three hundred and thirty days, does not impress one with any great ideas of magnificence; yet it is 113 feet high, and certainly forms a great mass of masonry. There is a chamber within, which is not always accessible, on account of the water. Some pieces of columns were found in digging at the base of the pyramid, two of which were put together and fixed at the angles of the building. I have no idea how they were originally applied, as there does not seem sufficient authority to supply a court and a surrounding portico. These meadows and the mount offer some amusement to the botanist in the spring; the mount especially is almost covered with orchideæ, amongst which _Ophrys apifera_ and _tenthredinifera_, and _Orchis papilionacea_, are the most abundant. I found here also _Ophrys hiulca_ and _arachnitis_ of the Flora Romana. Our next object is the brick arch of San Lazzaro, through which the road passes, though it is filled up nearly to its springing. There are several substructions at the foot of the hill, which appear to have belonged to the same edifice, but what that was, nobody knows.