The Piscinæ 34 Source of the Marcia ib. _Specus_ carried along the valley of the Anio 35 Principal source in the Acqua Serena ib. Old _Specus_ under water, discovered in 1869 36 —— It crossed the river at S. Cosimato ib. —— and again in the Valley of the Arches, above Tivoli, on a bridge ib. _Specus_ and reservoir in the Promenade of Carciano, below Tivoli ib. Reservoir faced with Cyclopean Masonry there 37 _Specus_ passes near Ponte di S. Antonio ib. After reaching the City it is divided into several branches ib. One along the Cœlian and over the Porta Capena to the Aventine 38 Another upon the old _agger_, and over the Porta Tiburtina to the Prætorian Camp ib. Excellent qualities of the Aqua Marcia ib. IV. TEPULA. Sources near Grotta Ferrata 39 _Specus_ joins the Marcia at the _Piscinæ_ 40 —— is carried into Rome on the Marcian arcade ib. _Castellum Aquæ_ for it near the Porta Tiburtina (S. Lorenzo) ib. V. JULIA. Sources on Mons Algidus (near Tusculum), Frascati, and Grotta Ferrata 41 _Specus_ passed near the Pagus Lemonius 42 —— on an arcade of rough stone ib. —— then through a tunnel in the valley ib. The Nymphæum of Alexander Severus, where the Trophies of Marius were hung, was _not_ for the Aqua Julia, though usually called so. It is at too high a level for that, and was for the Claudia and Anio Novus united 43 _Cippi_ of _the three_ Aqueducts, found in 1869, near the railway station 45 Remains of a reservoir near the Porta Chiusa, found in 1869 ib. VI. VIRGO (AQUA DI TREVI). Passages from Frontinus 46 Sources on the Via Collatina ib. _Specus_ subterranean, but easily traced by the line of respirators 47 —— It follows the old road towards the Porta Maggiore 48 —— but turns to the north and enters Rome through the Pincian Hill, under the Villa Medici ib. —— It supplies the lower town and the fountain of Trevi ib.