Page:Popular Science Monthly Volume 33.djvu/237

Rh in the neighborhood. Not far off to the south are the borax springs that supply Europe, the nearest being at Monte Arboli. Returning to the main line a little farther south is San Vincenzo, where a cordierite trachyte occurs, and in the works for lead and zinc near by toward Campiglia fine specimens of botryoidal bustamite are to be found.

Soon another line goes off to our left to Monte Amiata, an extinct volcano, whose lava contains interesting glass balls. It has recently been thoroughly described by an American, J. F. Williams ("Neues Jahrbuch," 1887). Half-way from here to Rome the volcanic tufa of the Campagna (25) comes in, and soon we are in sight of St. Peter's. There are collections in the university, but more modern ones at the rooms of the "Comitate Geologico," not very far from the railway-station in the modern quarter. On the Campagna the Roman cement—pozzuolana—diggings should be noticed, and we should go far enough on the Appian Way to visit the quarries in the melilith basalt of the Capo di Bove, whose cavities abound in tiny crystals of melilith, apatite, nepheline, etc. Monte Mario is well known for Pliocene fossils, and from Tivoli comes the famous travertine building-stone of Rome. The region of the Alban Lake affords pretty excursions. The workmen have leucite crystals.

Lago Bolsena is interesting but hard to get at. So on to Naples, where an Englishman, Dr. Lavis, is the present authority (23) on Vesuvius and Monte Somma, and has a fine collection. We should not fail to notice that east of Naples is another volcanic district, in type, time, and products of eruption quite distinct from Vesuvius, the Phlegræan fields, the front garden of the infernal regions, according to Virgil.

Armed with a permit from the palace at Naples, we visit the beautiful park crater of Astroni. The way leads past the famous Grotto del Cane, along the Lago d'Agnano, once a lake, now drained. On the road to Pozzuoli, where the Serapeum has had literally so many ups and downs, is the Solfatara, another smaller but livelier crater. A steam-tramway also connects Pozzuoli and Naples, and this may be made the starting-point of a second excursion among further craters. Lake Avernus, etc., which should certainly include a climb up Monte Nuovo, newest of mountains. May you be more fortunate than I, and have a chance to go farther and visit Etna and Sicily! But most of us must now return. Before we leave, one last warning: don't lay out too much for a day's work near Naples, Water is scarce and bad, wine is not good for walkers, and the climate is relaxing.

On the way back from Rome we will follow the central trough of the Arno and Tiber, which, near the water-shed where the water was dubious which way to go, was for a long time very