The floor of this old channel
The course of the stream below the mouth of the tunnel may be traced for some distance by scarps in the ice above, formed by the settling of the roof. Some of these may be traced in the illustrations. When the roof of the tunnel collapses so completely as to obstruct the passage, a lake is formed above the tunnel, and when the obstruction is removed the streams draining the glacier are flooded. At the mouth of the tunnel there are always confused noises and rhythmic vibrations to be heard in the dark recesses within. The air is filled with pulsations like deep organ notes. It takes but little imagination to transform these strange sounds into the voices and songs of the mythical inhabitants of the nether regions. Toward the right of the tunnel, as shown on plate 14, there appears a portion of the former river bed, now abandoned, owing to the cutting across of a bend in the stream. The floor of this old channel is mostly of clear, white ice, and has a peculiar, hummocky appearance, which indicates the direction of the current that once flowed over it. A portion of the bed is covered with sand and gravel, and along its border are gravel terraces resting on ice. These occurrences illustrate the fact that rivers flowing through channels of ice are governed by the same general laws as the more familiar surface streams. After examining this glacial river, during our first excursion on the Lucia glacier, we reached its western banks by crossing above the upper archway. Traversing the sand plain to the westward, we came to another stream of nearly equal interest, flowing along the western margin of the glacier, past the end of the deep gorge called Floral pass. A small creek, flowing down the pass, joins the stream and skirts the glacier just below the mouth of a wild gorge on the side of the main valley. This stream once flowed along the border of the Lucia glacier when it was much higher than now, and began the excavation of a channel in. the rock, which was retained after the surface of the glacier was lowered by melting. It still flows in a rock-cut channel for about a mile before descending to the border of the glacier as it exists at present. The geologist will see at once that this is a peculiar example of superimposed drainage. The gorge cut by the stream is a deep narrow trench with rough angular cliffs on either side, and is a good example of a water-rut canon. When the Lucia glacier melts away and leaves the broad-bottomed valley clear of ice, th.e deep narrow gorge on its western side, running parallel with its longer axes, but a thousand feet or more above its bottom, will remain as one of the evidences of a former ice invasion. During our reconnoissance we turned back at the margin of the second river, but a day or two later reached the same point with the camp hands and camping outfit, and, placing a. rope from, bank to bank, effected a crossing. Our next camp was in Floral pass. From there we occupied a topographical station on the summit of the Floral hills, and made another reconnoissance ahead, across the Hayden glacier,* to the next mountain spur.
