Before I close this letter I must give you an account of another excursion, or rather of two excursions, each of a single day, down to Ostia. I do not undertake in these expeditions to describe everything that I see. Many of the objects are so similar that they would appear the same in description, though we always find difference enough to interest us in the reality. I might indeed have said something about the reservoir of Marius at Albano, and about the prætorian camp, attributed to Domitian, in the same neighbourhood, one of the stones of which is fifteen feet and a half long, and where Nibby is sure that there were four towers, for he saw traces of one of them; but I shall leave these, and a hundred other things which would scarcely interest you. My first trip to Ostia was on the 15th of April, a fine frosty morning, when there was ice on the puddles and at the edges of the brooks, but elsewhere everything was dry and dusty. The corn on the hills began to look yellow for want of rain, but that in the valleys was strong and healthy, and the hawthorn was just coming into flower in spite of the frost, which has come this year so much after its usual time. The road follows the valley of the Tiber, which is bounded by low hills, descending pretty steeply towards the stream; sometimes close to the river, sometimes receding from it, and leaving a wide and fertile plain. In the first part of the way it is well cultivated, but thinly inhabited; farther on, cultivation diminishes, and ceases when we ascend an advancing and conspicuous point of these hills, and descend into the remains of the sacred wood. It is here mere brushwood, but at a distance to the left we may perceive plenty of large trees. The cutting down of this sacred wood is said to have occasioned the mal aria to extend much more about Rome; but this mal aria is a very mysterious affair, and many inconsistent stories are told about it. The letting in the sea breezes has ruined the country; yet the sea-shore is more healthy than the land immediately behind it. Within the walls of Rome some houses are said to be totally uninhabitable in the summer, while others, a hundred yards distant, because they are a little higher, a little farther from the Tiber, or from the country, or more surrounded by other houses, are pronounced entirely free. Out of Rome, and in the less inhabited parts within its walls, the hills are reckoned better than the valleys; but in modern Rome, the lower part of the city is more healthy than the upper. The Romans fancy that turning up the ground, in order to make a public garden on Monte Pincio, has made the street below it unhealthy. This mal aria occurs in the heats of summer, and in autumn, but this spring has been very unhealthy in Rome, and I believe, all over Italy. Among the numerous causes to which the mal aria is attributed, the alternation of hot days and cold nights, or rather perhaps, of hot sun and cold wind,