Descending from the church of San Gregorio towards the south-west, we reach the southern angle of the Palatine, where the Septizonium formerly stood. It was destroyed by Sixtus the Fifth, and the columns, and probably some of the other materials, were employed in the Vatican. Antiquaries have imagined from the name, that seven successive orders must have been employed here, not reflecting that three orders would produce the appearance of seven zones or bands. First, the pedestal on which the whole is placed, which forms a solid mass; then a range of columns and voids; then another solid mass composed of the entablature of the first order, and the continued plinth and pedestals of the second. The fourth zone would be composed of the columns of the second order, and the voids between them; these open bands having always a different character and appearance from the solid ones, however composed. The fifth of the entablature and pedestals as before, or if there were no pedestals, by the entablature alone. These solid zones would have the appearance of being striped horizontally by the shadows of the mouldings, while the columns would give to the open bands the appearance of being striped vertically. Sixthly, the columns of the third order. Seventhly, the entablature, and whatever might crown the edifice, and this disposition is exactly correspondent with the idea we entertain of the building from old engravings. In this part, and along the south-western side of the hills, the remains on the Palatine are very considerable, consisting of lofty piers, and extended arches, but every trace of ornamental architecture has disappeared. Here also we find all that is to be seen of the Circus Maximus, _i. e._ the general form, favoured by the natural shape of the ground between the Palatine and Aventine hills. I shall not occupy you with any long dissertation on the ancient circus, or on the obscure god Consus, to whom it was dedicated. You know that the general form, in spite of the name, was that of an oblong, with one semicircular end; the other end was not straight, but somewhat curved and inclined, in order as much as possible to put each chariot which started from it, in an equally advantageous situation, and the _spina_ was not placed either precisely in the centre, or exactly parallel to the sides, but in such a manner as to form a road continually narrower as the chariots proceeded in the circuit. A few burrs of rubble-work, and fragments of nearly buried arches, the foundations of the sedili, are all the remains. And now, leaving the baths of Caracalla and the tomb of the Scipios, for the subjects of a future letter, we will cross the Aventine, a hill divided into two summits, on which are the two churches of Santa Prisca, and Santa Saba, and a ruined convent, from which there is a fine view of Rome, and which is itself a very picturesque object. Both these churches contain ancient columns; that of Santa Saba is said in the guide-book,