The romance of the grove of Egeria was, however, dispelled when the valley was turned into a place of imprisonment for the Jews.  Domitian drove them out of the Ghetto, and shut them up here, with only a basket and a wisp of hay for each person, to undergo unheard-of privations and miseries.  The Horticultural Gardens, where the shrubs and plants are grown that ornament the public squares and terraces of the city, now occupy the site of the celebrated grove.  The shrill scream of the railway whistle outside the gate, and the smell of the gas-works near at hand—­these veritable things of the present century—­are fatal to all enchantments, and effectually dissipate the spell of the muses and the mystic fragrance of the Egerian solitude.  But wonderful is the persistence of a spring in a spot.  Continually changing, it is the most changeless of all things.  For ever passing away, it is yet the most steadfast and enduring.  Derived from the fleeting vapour—­the emblem of inconstancy—­it outlasts the most solid structure of man, and continues to well up its waters even when the rock beside it has weathered into dust.  The Fountain of Egeria flows to-day in the hollow of the Coelian Hill as it flowed nigh three thousand years ago, although the muses have fled, and the deities Picus and Faunus, which Numa entrapped in the wood of the Aventine, have gone back to their native skies with Jupiter; and Mammon and Philosophy have exorcised that unseen world which once presented so many beauties and wonders to the imagination of man.

A little farther on to the right, a side path, called the Via Antonina, leads up to the stupendous ruins of the Baths of Caracalla, a mile in circumference, and covering a space of 2,625,000 square yards.  The walls, arches, and domes of massive brickwork hanging up in the sky,—­the fragments of sculpture and splendid mosaic pavements belonging to these baths,—­produced a deeper impression upon my mind than even the ruins of the Colosseum.  With the form and majesty of the Colosseum, owing to its compactness and unity, pictures and other representations have made us familiar from infancy, so that it excites no surprise when we actually visit it; but the Baths of Caracalla cannot be pictorially represented as a whole, on account of their vast variety and extent, and therefore we come to the spectacle wholly unprepared, and are at once startled into awe and astonishment.  Notwithstanding the wholesale pillage of centuries, enough in the way of chambers and baths, marble statues, pillars, and works of art, still remains in this mountainous mass of masonry to witness to the unparalleled luxury by which the strength of the Roman youth was enervated, and the foundations of the empire sapped.  Shelley wrote on the summit of one of the arches his “Prometheus Unbound;” and certainly a fitter place in which to seek inspiration for such a theme could not be found.