up the mountain, the gray rocks are principally covered with the Spanish broom, and a large coarse grass (_Arundo ampelodesmus_) though not without a mixture of the humbler growth of cistuses and helianthema. All this sounds very beautiful, and in fact it is so, but the features are so much hid by the continued grove of olive-trees, that they are almost lost in the effect of the general scenery, and you may pass through the country, and see very little of it. This digression has entirely carried me away from the usual tour, which was the first I made, and which I had begun to describe to you. I left it just at the villa of Quintilius Varus. From every opening in this part of the walk you have a view of the long portico of the villa of Mæcenas, crowning the opposite hill, on lofty arched substructions, and of the Cascatelle, rushing down the slope in sheets of foam, into the valley beneath. We may leave the road soon after the bifurcation, where I took the right-hand track, and keeping still more to the left, than the left-hand path, descend to the bottom of the hill, to enjoy more fully the view of the Cascatelle. The prospect varies at every step of the descent. We first lose the distant Campagna, which is disclosed from the upper part of the slope, and soon afterwards the olive-groves beyond the villa of Mæcenas; while the villa itself seems more majestically placed; the water falling in various directions becomes of more consequence; and the rich woods of the high bank opposite to us display all their beauties. The great Cascatella furnishes a considerable mass of water, but though the fall is much higher than any that I have before described, yet as it occupies a much more open situation, the character of the scenery has less of the sublime than that about the grotto of the Syren, and more of the beautiful. There are a great many other fragments of villas about here, but as they have nothing very characteristic, I shall not stop to enumerate them. We will therefore pass on to the Ponticelli, or Ponte Acquorio, but before crossing it, I will mention a beautiful spring called _Acqua Aurea_, which rises by the side of the river, just above the bridge, and gives to it the latter name: the former is thought to be a corruption of Pons Gellius. You are told that a scheme was once in agitation to carry this water to Rome, but on taking its level, it was found to be too low. This does not seem to me at all probable. The Teverone is a pretty brisk stream; and in a course, which, including the windings, must equal twenty-five miles, it can hardly fall less than 75 feet, in which case the _Acqua Aurea_ might enter Rome, not indeed at the Porta Maggiore, but 50 feet above the level of the Tiber. The Lea, from Hertford to Stratford, runs about the same distance, and I think not more rapidly, and though we have to remount the Thames from thence to London, we find the reservoir of the New River 84 feet above the tide.