The song of the nightingale is to be heard, without intermission, for fifteen days and nights, continuously, when the foliage is thickening, as it bursts from the bud; a bird which deserves our admiration in no slight degree. First of all, what a powerful voice it has in so small a body! its note, how long, and how well sustained! And then, too, it is the only bird the notes of which are modulated in accordance with the strict rules of musical science. At one moment, as it sustains its breath, it will prolong its note, and then at another, will vary it with different inflections; then, again, it will break into distinct chirrups, or pour forth an endless series of roulades. 207 Then it will warbl............