These are the most essential points in the structure of an amphitheatre. Many things connected with the arrangements, however, still remain obscure, and the lower part of the Colosseum has not yet been sufficiently excavated. It is, for example, still uncertain in what manner it was contrived to introduce the wild beasts into the arena. All the explanations which have been proposed are unsatisfactory. Excavations have indeed been made, but have been discontinued partly from a fear of weakening the building, which point certainly is not to be overlooked, on account of the many earthquakes, and partly on account of erroneous suppositions, because people could not understand that the arena was moveable. Another reason why the excavations are not continued, is the belief that at one time there was an altar in the arena, and that accordingly the ground is sacred through the blood of the martyrs. Such perverse notions are obstacles to the discovery of truth. Another amphitheatre, the _amphitheatrum castrense_, was close to the wall; Procopius calls it _Vivarium_. I shall now proceed to speak of the _thermae_. Public baths existed at Rome from the earliest times. Southern countries really require them, and they were universally used until late in the middle ages. Under Gregory I., one of the greatest and most excellent men of his period, whose government was distinguished for its beneficial measures, though he did not reign as a sovereign, Rome was already quite deserted; still, from one of his letters, I have learned that the use of baths was then quite common. Pope Hadrian I.,[28] likewise a very great man, restored the Aqua Claudia, which had been neglected, for the purpose of supplying the baths with water. Gregory I. states, that in his time many people considered it sinful to bathe on a Sunday; but he himself, who was more clear-sighted than his flock, issued a proclamation[29] advising the people not to be so foolish as to allow themselves to be prevented by such a prejudice. This is a proof that baths were then still in general use. In Germany, too, they were more common in the middle ages than they are now. Such _balnea_ or _balneae_ were very popular in ancient Rome even before the manners of the Greeks had commenced exercising their influence. _Thermae_ (θερμαί) were first built under Augustus; but we must not infer from this, that previously people bathed in cold water in the city, for whenever they wished to do this, they plunged into the Tiber. I explain the name _thermae_ in the following manner:—It had become customary at Baiae and other watering places to combine warm baths with the use of the mineral waters and with sea-bathing: the life in those places was like that in our watering-places: people frequented them for the purpose of diverting their minds and taking care of their bodies. Greeks (commonly called _Graeculi_) were not wanting to provide amusements of every description with the same industry which Italians