On another day the train bore us around the famous "Loop" to Silver Plume. In the beautiful pine grove at the terminus of the railway there were many birds--siskins, chipping sparrows, western robins and ruby-crowned kinglets; and they were making the place vocal with melody, until I began to inspect them with my glass, when they suddenly lapsed into a silence that was as trying as it was profound. By and by, discretion having had her perfect work, they metaphorically came out of their shells and permitted an inspection. Above the railway I saw one of the few birds of my entire Rocky Mountain outing that I was unable to identify. That little feathered Sphinx--what could he have been? To quote from my note-book, "His song, as he sits quietly on a twig in a pine tree, is a rich gurgling trill, slightly like that of a house-wren, but fuller and more melodious, with an air about it that makes me feel almost like writing a poem. The bird is in plain view before me, and I may watch him either with or without my glass; he has a short, conical bill; his upper parts are gray or olive-gray; cervical patch of a greenish tinge; under parts whitish, spotted with dusk or brown. The bill is white or horn-color, and is quite heavy, I should say heavier than that of any sparrow I know. The bird continued to sing for a long time and at frequent intervals, not even stopping when the engine near at hand blew off steam, although he turned his head and looked a little startled." I saw this species nowhere else in my Colorado rambles, and can find no description in the systematic manuals that helps to clear up the mystery, and so an _avis incognita_ he must remain for the present. Has mention been made of a few house-finches that were seen in Georgetown? Only a few, however, for they prefer the towns and cities of the plain. Several house-wrens were also seen in the vicinity of the Georgetown Loop as well as elsewhere in the valley. The "Loop," although a monumental work of human genius and daring, has its peculiar attractions for the student of natural history, for in the cañon itself, which is somewhat open and not without bushy haunts, and on the precipitous mountain sides, a few birds set up their Lares and Penates, and mingle their songs of domestic felicity with the roar of the torrent and the passing trains. Darting like zigzag lightning about the cliffs, the broad-tailed humming-bird cuts the air with his sharp, defiant buzz, until you exclaim with the poet: "Is it a monster bee, Or is it a midget bird, Or yet an air-born mystery That now yon marigold has stirred?" [Illustration: "_Solo singing in the thrush realm_"]