. Nature-study; a manual for teachers and students. Nature study. NATURE-STUDY They consist of a hollow quill stem and a solid elonga- tion, the shaft. On the shaft at each side are fine branches called barbs. These are again divided, and sometimes subdivided into smaller branches called barbulcs and proc- esses . These barbules and processes interlock to form a stiff, resisting surface. The shaft and barbs form the vane. Besides these feathers tlicre are various mod- ifications in dif- ferent birds,such as the beau- tiful plumes on the heads, chest, shoulders, hips, etc., of ostriches, herons
. Nature-study; a manual for teachers and students. Nature study. NATURE-STUDY They consist of a hollow quill stem and a solid elonga- tion, the shaft. On the shaft at each side are fine branches called barbs. These are again divided, and sometimes subdivided into smaller branches called barbulcs and proc- esses . These barbules and processes interlock to form a stiff, resisting surface. The shaft and barbs form the vane. Besides these feathers tlicre are various mod- ifications in dif- ferent birds,such as the beau- tiful plumes on the heads, chest, shoulders, hips, etc., of ostriches, herons, and other birds; the hair-hke tuft on the breast of the turkey cock, etc. These are used mainly for decoration. Birds raise and maintain themselves in the air not by their relative lightness (as is the case with a balloon), but by the reaction of the air against the powerful wing strokes, or else by the force of winds against the wing and tail surfaces. Most birds that flap their wings in flight use the first principle, while the hawk, which circles around high in the air without apparently a stroke of the wing, and only. Fig. i6. Chimney Swift. (Not :\ s^^â allo^ Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Holtz, Frederick Leopold, 1870-. New York, C. Scribner's Sons
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