. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 1. cross-section is usually repi'esented as in Figure 1, in which the depth of the rock-floored valley is made greater than that of the new valley carved in the drift filling. A notable feature of such terrace sections is that the open space measiu*ed across the valley between the scarps of the low-level terraces is narrower than that between the scarps of the high-level terraces ; and this fact has frequently given rise to the supposition that the volume of our streams to-day is less than that. Fig. 2. of the st
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 1. cross-section is usually repi'esented as in Figure 1, in which the depth of the rock-floored valley is made greater than that of the new valley carved in the drift filling. A notable feature of such terrace sections is that the open space measiu*ed across the valley between the scarps of the low-level terraces is narrower than that between the scarps of the high-level terraces ; and this fact has frequently given rise to the supposition that the volume of our streams to-day is less than that. Fig. 2. of the streams by which the high-level terraces were carved. It will however be shown from what follows that the characteristic cross-section of a terraced valley in which the river has not yet reached rock bottom exhibits few stepping terraces, and is fairly represented by Figure 2 ; while if stepping terraces are present a characteristic section, on which the most significant points for a mile or more up and down the valley are projected, would show that the base of many of the terraces is determined for short distances (ten to fifty feet) by a rock ledge, as in. 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 Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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