Many persons have a mania for pigeons—building towns for them on the top of their roofs, and taking a pleasure in relating the pedigree and noble origin of each. Of this there is an ancient instance which is very remarkable; Lucius Axius, a Roman of the equestrian order, shortly before the Civil War of Pompey, sold a single pair for four hundred denarii, so Marcus Varro tells us. Countries even have gained renown for their pigeons; it is thought that those of Campania attain the largest size. CHAPTER XIX. DIFFERENT MODES OF FLIGHT AND PROGRESSION IN BIRDS. Mentioning the flight of the pigeon leads me to consider that of other birds. All other animals have one determinate mode of progression, which in every kind is always the same; birds alone have two modes of moving—on the ground, and in the air. Some of them walk, such as the crow, for instance; some hop, as the sparrow and the blackbird; some run, as the partridge and the woodhen; while others throw one foot before the other, like the stork and the crane. Then again, in their flight, some birds expand their wings, and poising themselves in the air, only move them from time to time; others move them more frequently, but then only at the extremities; while others expand them so as to expose the whole of the side. On the other hand, some fly with the greater part of the wings kept close to the side; and some, after striking the air once, others twice, make their way through it, as though pressing upon it enclosed beneath their wings; other birds dart aloft in a vertical direction, others horizontally, and others come falling straight downwards. You would almost think that some had been hurled upwards with a violent effort, and that others had fallen straight down from aloft; while others still are seen to spring forward in their flight. Ducks alone, and the other birds of that kind, in an instant raise themselves aloft, taking a spring from the spot where they stand straight upwards towards the heavens; and this they can do directly from the water. They are the only birds that can make their escape from the pitfalls which we employ for the capture of wild beasts. The vulture and the heavier wild birds can only fly after taking a run, or else by commencing their flight from an elevated spot. They use the tail by way of rudder. There are some birds that are able to see all around them; others have to turn the neck to do so. Some of them eat what they have seized, holding it in their feet. Many, as they fly, utter some cry, while others are always silent. Some fly with the breast half upright, others with it held downwards, others fly obliquely, or side-ways, and others follow the direction of the bill. The fact is, that if we were to see several kinds at the same moment, we should not suppose that they were adapted to the same element.