Studies in the Sierra. No. III. - Ancient Glaciers and Their Pathways.

• Main Author: Muir, John
• Format: Text
• Language: English
• Published: Scholarly Commons 1874
• Subjects: John Muir; Bibliography; Kimes; William F. Kimes; Maymie B. Kimes; pamphlets; journal articles; speeches; writing; naturalist; annotation; Clark Mountains; Dome The; Glacier Point; Indian; Jagged; Lyell Glacier; Mount Clark; Noble Glacier; Ice Sheet
• Online Access: https://scholarlycommons.pacific.edu/jmb/82; https://scholarlycommons.pacific.edu/cgi/viewcontent.cgi?article=1081&context=jmb

1874-] STUDIES IN THE SIERRA. Beneath their wings, awaiting night; Then great striped lizards, with eyes bright As jet, shot through the brown, thin grass Made gray with dust of alkali, Then stopped, then looked, then lifted high On crooked legs, and looked and looked. 67 STUDIES IN THE SIERRA. NO. III.-ANCIENT GLACIERS AND. THEIR PATHWAYS. THOUGH the gigantic glaciers of the Sierra are dead, their history is indelibly recorded in characters of rock, mountain, canon, and forest; and, although other hieroglyphics are being incessantly engraved over these, "line upon line" the glacial characters are so enormously emphasized that they rise free and unconfused in sublime relief, through every after inscription, whether of the torrent, the avalanche, or the restless heaving atmosphere. In order to give the reader definite conceptions of the magnitude and aspect of these ancient ice-rivers, I will briefly outline those which were most concerned in the formation of Yosemite Valley and its cafion branches. We have seen (in the previous paper) that Yosemite received the simultaneous thrust of the Yosemite Creek, Hoffmann, Tenaya, South Lyell, and Illilou- ette glaciers. These welded themselves together into one huge trunk, which swept down through the valley, receiving small affluents in its course from Pohono, Sentinel, and Indian canons, and those on both sides of El Capitan Rock. At this period most of the upper portions of the walls of the valley were bare; but during its earlier history, the wide mouths of these several glaciers formed an almost uninterrupted covering of ice. All the ancient glaciers of the Sierra fluctuated in depth and width, and in degree of individual ity, down to the .latest glacial days. It must, therefore, be distinctly borne in mind that the following sketches of these upper Merced glaciers relate only to their separate condition, and to that phase of their separate condition which they presented toward the close of the period when Yosemite and its branches were works nearly accomplished. YOSEMITE CREEK GLACIER. The broad, many-fountained glacier to which the basin of Yosemite Creek belonged, was about fourteen miles in length by four in width, and in many places was not less than a thousand feet in depth. Its principal tributaries issued from lofty amphitheatres laid well back among the northern spurs of the Hoffmann range. These at first pursued a westerly course; then, uniting with each other and absorbing a series' of small affluents from the Tuolumne divide, the trunk thus formed swept round" to the south in a magnificent curve, and poured its ice into Yosemite!-in' cas- ' cades two miles wide. This broad glacier formed a kind of wrinkled ice-cloud. As it grew older, it became more regular and river-like; encircling peaks overshadowed its upper fountains, rock islets rose at intervals among its shallowing currents, and its bright sculptured banks, nowhere overflowed, extended in massive simplicity all the way to its mouth. As the ice-winter drew near a close, the 68 STUDIES IN THE SIERRA. 4\. i u . main trunk, becoming torpid, at length wholly disappeared in the sun, and a waiting multitude of plants and animals entered the new valley to inhabit the mansions prepared for them. In the meantime the chief tributaries, creeping slowly back into the shelter of their fountain shadows, continued to live and work independently, spreading moraine sail for gardens, scooping basins for lakelatSj -and leisurely completing the sculpture of their fountains. These also have at-last vanished, and the whole basin is now full of light. Forests flourish luxuriantly over all its broad moraines, lakes and meadows nestle among its domes, and a thousand flowery gardens are outspread along its streams. HOFFMANN GLACIER. .' j a , The short, swift-flowing Hoffmann Glacier Noffered a striking contrast to the Yosemite Creek, in the energy and directness of its movements, and the general tone and tendencies of its life. The erosive energy of the latter was diffused over a succession of low bowlder-like domes. Hoffmann Glacier, on the contrary, moved straight to its mark, making a descent of 5,000 feet in about five, miles, steadily deepening and contracting its current, and finally thrusting itself against the upper portion of Yosemite in the form of a wedge of solid ice six miles in length by four in width. The concentrated action of this energetic glacier, combined with that of the Tenaya, accomplished the greater portion of-the work of the disinterment and sculpture of the great Half Dome, North Dome, and the adjacent rocks. Its fountains, ranged along the southern slopes of the main Hoffmann ridge, gave birth to a series of flat, wing-shaped tributaries, separated from one another by picturesque walls built of massive blocks, bedded and jointed like masonry. The story of its death is not unlike that of the Yosemite Creek, though the [July, declivity of its channel and .equal exposure to sun-heat prevented any considerable portion from passing through a .torpid condition. It was first burned; off on its lower course; then, creeping slowly back, lingered awhile at the base of its mountains to finish their sculpture, and encircle them with a zone of moraine soil for gardens and forests. - The gray slopes of Mount Hoffmann are singularly barren in aspect, yet the traveler who is so fortunate as to as- cend them will find himself in the very J loveliest gardens of the Sierra. The lower banks and slopes of the basin are plushed with chaparral rich in berries and bloom—a favorite resort for bears while the middle region is planted with the most superb forest of,silver-fir I ever beheld. Nowhere are the cold footsteps of ice more warmly covered with light and life. TENAYA GLACIER. The rugged, strong-limbed Tenaya Glacier was about twelve miles long, and from half a mile to two and a half miles wide. Its depth varied from near 500 to 2,000 feet, according as its current was outspread in many channels or compressed in one. Instead of drawing its supplies directly from the summit fountains, it formed one of the principal outlets of the Tuolumne mer de glace, issuing at once from this noble source, a full-grown glacier two miles wide and more than a thousand feet deep.\It flowed in a general southwesterly direction, entering Yosemite at the head, between Half and North domes. In setting out on its life-work- it moved slowly, spending its strength in ascending the Tuolumne divide, a'nd in eroding a series of parallel sub-channels leading over into the broad, shallow-basin of Lake Tenaya. Hence, after uniting its main current, which had been partially separated in crossing the divide, and receiving a swift-flowing af- 1874-3 STUDIES IN THE SIERRA. 69 fluent from the fountains of Cathedral Peak, it set forth again with renewed vigor, pouring its massive floods over the south-western rim of the basin in a series of splendid cascades; then, crushing heavily against the ridge of Cloud's Rest, curved toward the west, quickened its pace, focalized its wavering currents, and bore down upon'Yosemite \Avith ka-wrrore concentrated energy. Toward the end of the ice-period, and while the upper tributaries of its Hoffmann companion continued to grind rock-meal for coming forests, the whole body of Tenaya became torpid, withering simultaneously from end to end, instead of dying gradually from the foot upward. ' Its upper portion separated into long parallel strips extending between the Tenaya basin and Tuolumne mer deglace. These, together with the shallow ice-clouds of the lake-basin, melted rapidly, exposing broad areas of rolling rock-waves and glossy pavements, on whose channelless surface water ran everywhere wild and free. There are rk very'extensive morainal accumulations of any sort in the basin. The largest occur on the divide, near the Big Tuolumne Meadows, and on the sloping ground north-west of Lake Tenaya.* For a distance of six miles from its mouth .the pathway of this noble glacier is a simple trough from 2,000 to 3,000 feet deep, countersunk in the solid granite, with sides inclined at angles with * Because the main trunk died almost simultaneously throughout its whole extent, we, of course, find no terminal moraines curved across its channels; nor, since its banks were in most places too steeply inclined for their deposition, do we find much of the two laterals. One of the first Tenaya glacierets was developed in the shadow of Yosemite Half Dome. Others were formed along the bases of Coliseum Peak, and the long, precipitous walls extending from near Lake Tenaya to the Big Tuolumne Meadows. The latter, on account of the uniformity and continuity of their protecting shadows, formed moraines of considerable length and regularity, that are liable to be mistaken for portions of the left lateral ntoiaine of the main glacier. the horizon of from thirty to fifty degrees. Above this its grand simplicity is interrupted by huge moutoneed ridges extending in the general direction of its length over into the basin of Lake Tenaya. Passing these, and crossing the bright glacial pavements that border the lake, we find another series of ridges, from 500 to 1,200 feet in height, extending over the divide to the ancient Tuolumne ice-fountain. Their bare moutoneed forms and polished surfaces indicate that they were overswept, existing at first as mere bowlders beneath the mighty glacier that flowed in one unbroken current between Cathedral Peak and the south-east shoulder of the Hoffmann range. NEVADA, OR SOUTH LYELL GLACIER. The South Lyell Glacier was less-m- fiuential than- the last, but longer and more symmetrical, and the only one of the Merced system whose sources extended directly to the main summits on the axis of the chain. Its numerous ice- wombs, now mostly barren, range side by side in three distinct series at an elevation above sea-level of from 10,000 to 12,000 feet. The first series on the right side of the basin extends from the Matterhorn to Cathedral Peak in anorth- westerly direction a distance of about twelve miles. The\ second series extends in the same direction along the left side of the basin in the summits of the Merced group, and is about six miles in length. The third is about nine miles long, and extends along the head of the basin in a direction at right angles to that of the others, and unites with them at their south-eastern extremities. The three ranges of summits in which these fountains are laid, and the long continuous ridge of Cloud's Rest, inclose a rectangular basin, leaving an outlet near the south-west corner opposite its principal neve fountains, situated in the dark jagged peaks of the Lyell 7o STUDIES IN THE SIERRA. [July, group. The main central trunk, lavishly fed by these numerous fountains, was from 1,000 to 1,400 feet in' depth, from. j three-fourths of a mile to'a mile and a half in width, and about'fifteen miles in length. It first flowed in a north-westerly direction for a few miles, then curving toward the left, pursued a westerly course, and poured its shattered cascading currents down into Yosemite between Half Dome and Mount Starr \ King. Could we have visited Yosemite'toward the close of the glacial period, we should have found its ice-cascades vastly more glorious than their tiny water representatives of the present hour. One of the most sublime of these was formed by that portion of the South Lyell current which descended the broad, rounded shoulder of Half-Dome. The whole glacier resembled an oak with a gnarled swelling base and wide- spreading branches. Its banks, a few miles above Yosemite, were adorned with groups of picturesque rocks of every conceivable form and mode of combination, among which glided swift-descending affluents, mottled with black slates from the summits, and gray granite blocks from ridges and headlands. One of the most interesting facts relating \fo the early history of this glacier is, that the lofty'cathedral spur forming the north-east boundary of its basin was broken through and overflowed- by deep ice-currents from the Tuolumne region. The scored and polished gaps eroded by them in their passage across the summit of the spur, trend with admirable steadiness-in~a~north-easter-ly.and southwesterly direction; a fact of great importance, considered in its bearings upon questj.ans_-r.elattng to the universal . ice-sheet. Traces of a similar overflow from the north - east occur on the edges of the basins of all the Yosemite glaciers. X The principal moraines of the basin occur in short, irregular sections scattered along the sides of the valleys, or spread in rough beds in levej portions of their bottoms, without manifesting subordination to any system whatever. This fragmentary condition is due to interruptions caused by portions of the sides of the valleys being too precipitous for moraine matter to rest upon, and to the breakings and down-washings of torrentsf; and avalanches of winter snow. The obscurity resulting from these causes is further augmented by forests and underbrush, making a patient study of details indispensable to the recognition of their.unity and simple grandeur. The south lateral moraine of the lower portion of the trunk may be traced about five miles, from the mouth, of the north tributary of Mount Clark to the cafion of Illilouette, though simplic 1 -ity of structure has in most places been prevented by the nature of the ground, and by the action of a narrow margin glacier which descended against it with variable pressure from cool, shadowy slopes above. The corresponding section of the right lateral, extending from the mouth of Cathedral tributary to Half Dome, is far more perfect in structure, because of the evenness of the groifnd, and because the ice-wing which curved against Q°ud's Rest and descended against it was fully exposed to the sun, and was, therefore, melted long before the main trunk, allowinguhe latter to complete the formation ofythis section of its moraine undisturbed. Some conception of its size, and general character may be obtained by following the Cloud's Rest and, Yosemite trafl, which crosses it obliquely, leading past several cross- sections made by small streams. A few slate bowlders from the Lyell group may be seen, but the main mass of the moraine is composed of ordinary granite and porphyry, the latter having been derived from Feldspar and Cathedral valleys. 1874-3 STUDIES IN THE SIERRA. 7i OStZS 72 STUDIES IN THE SIERRA. [July, The elevation of the top of.the moraine near Cathedral tributary is about 8,100 feet; near Half Dome, 7,600. It rests upon the side of the valley at angles varying from fifteen to twenty-five degrees, and in many places is straight and uniform as a railroad embankment. The greatest depth of the glacier between Cloud's Rest and Mount Starr King, measuring from the highest points of its lateral moraines, was 1,300 feet. The recurrence of ridges and terraces on its sides indicate oscillations in the level of the glacier, probably caused by clusters of.cooler or snowier seasons which no doubt diversified the great glacial winter, just as clusters of sunny or stormy days .occasion fluctuations in the level of the streams and prevent monotony in our annual winters. When the depth of the South Lyell Glacier diminished to about 500 feet, it became torpid, on ac-. count of the retardation caused by the roughness and crookedness Of its channel. But though it henceforth made no farther advance of its whole length, it possessed feeble vitality-r-jn small sections, of exceptional slope or depth, maintaining, a squirming and swedging motion, while it lay dying like a wounded serpent. The numerous fountain wombs continued,fruitful long after the lower valleys were developed and vitalized with sun-heat. These gave rise to an imposing series of short residual glaciers, extending around three sides of tjife, quadrangular basin, a distance of twenty-four miles. Most of them have but recently succumbed to the demands of the changing seasons, dying in turn, as determined by elevation, size, and exposure. A few still linger in the loftiest and most comprehensive shadows, actively engaged upon the last hieroglyphics which will complete the'history of , the South Lyell Glacier, forming one I of the noblest and most symmetrical sheets of ice manuscript in the whole \ Sierra. ILLILOUETTE. The broad, shallow glacier that inhabited the basin of Illilouette more resembled a lake than a river, being nearly half as wide as it was long. Its greatest length was about ten miles, and its depth perhaps nowhere much exceeded 700 feet. Its chief fountains were ranged along the western side of the Merced spur at an elevation of about 10,000 feet. T-hes* gave, birth to magnificent affluents,,flowing in a westerly direction for several miles, in full independence, and uniting, near the centre of the basin. The principal trunk curved northward, grinding heavily against the lofty wall forming its left bank, and finally poured its ice into Yosemite by the South Canon between Glacier Point and Mount Starr King. -A-lkthe, phenomena relating to glacial action in this basin are remarkably simple and orderly, on account of the sheltered positions occupied by its principal fountains with reference to the unifying effects of ice-currents from the main summits of the chain. A fine general view, displaying the principal moraines sweeping out into the middle of the basin from Black, Red, Gray, and Clark mountains may be obtained from the eastern base of the cone of Starr King. The right lateral of the tributary which took its rise between Red and Black mountains is a magnificent piece of ice-work. Near the upper end, where it is joined to the shoulder of Red Mountain, it is 250 feet in height, and displays three well-marked terraces. From the first to the second of these, the vertical descent is eighty-five feet, and inclination of the surface fifteen degrees; from the second to the third, ninety- five feet, and inclination twenty-five degrees and from the third to the bottom of the channel, seventy feet, made at an angle of nineteen degrees. The smoothness of the uppermost terrace shows that it is considerably more ancient than the others, many of the blocks of which i874-3 STUDIES IN THE SIERRA. 73 it was composed having crumbled to dotted with junipers and silver-leafed sand. pines, and separated by dark, feathery A few miles farther down, the moraine base - fringes of fir. has an average slope in front of about The ice-plows of Illilouette, ranged twenty-seven degrees, and an elevation side by side in orderly gangs, have fur- above the bottom of the channel of 666 rowed its rocks with admirable uniform- feet. More than half of the side of the ity, producing iw4gat-ing channels for a channel from the top is covered with brood of wild streams, and abundance moraine matter, and overgrown with a of deep, rich soils, adapted to every re- dense growth of chaparral, composed quirement of garden and grove. No of manzanita, cherry, and castanopsis. other section of the Yosemite uplands Blocks of rose-colored granite, many of is in so high a state of glacial cultiva- them very large,, occur at.intervals all tion. Its clustering domes, sheer walls, the way from the weste-cnJiaaeof Mount and lofty towering peaks, however ma- Clark to Starr King, indicating exactly jestic in themselves, are only border the covurse pursued by the ice when the adornments, submissively subordinate to northtdivide of the basin was overflow- their sublime garden centre. The ba- ed, Mount Clark being the only source sins of Yosemite Creek, Tenaya, and whence they could possibly have been South Lyell, are pages of sculptured derivfitl. rocks embellished with gardens. The Near the middle of the basin, just Illilouette basin is one grand garden where the regular moraines flatten out embellished with rocks, and disappear,, there is outspread aV/ Nature manifests her love for the smooth gravel slope, planted with the/ number five in her glaciers, as well as olive-green Arctostaphylos glauca so as in the petals of the flowers which she to appear in the distance as a delightful plants in their pathways. These five meadow. Sections cut by streams show Yosemite glaciers we have been sketch- it to be composed of the same material ing are as directly related to one anoth- as the moraines, but finer and more er, and for as definite an object, as are water-worn. The main channel, which the organs of a plant. After uniting in is narrow at this point, appears to have the valley, and expending the down- been dammed up with ice and terminal thrusting power with which they were moraines, thus giving rise to a central endowed by virtue of the declivity of lake, at the bottom of which moraine their channels, the trunk flowed up out matter was re-ground and subsequently of the valley without yielding much corn- spread and leveled by the impetuous pliance to the crooked and comparative- action of it's outbreaking waterS. The, ly small river cafion extending in a gen- southern boundary of the basin is a strikingly perfect wall, extending sheer and unbroken from Black Mountain* to Buena Vista Peak, casting a long, cool shadow all through the summer for the protection of fountain snow. The north- eral westerly direction from the foot of the main valley. In effecting its exit a considerable ascent was made, traces of which are to be seen in the,upward slope of the worn, rounded extremities of the valley walls. Down this glacier- ern rim presents a beautiful succession j constructed grade descend both the of smooth undulations, rising here and \ Coulterville and Mariposa trails; and we there to a dome, their pale gray sides J niight further observe in this connection that, because the ice-sheet near the pe- * This mountain occurs next south of Red Mount- . , c , . ,. . . , , .-.-■ -. ' :, \- _, , nod of transition to distinct glaciers am, and must not be confounded with the Black . to Mountain six miles farther south. flowed SOUtll - westerly, the SOUth lipS of Vol. 13. — 6. 74 STUDIES IN THE SIERRA. [July, all Yosemites trending east and west, other conditions being equal, are more heavily eroded, making the construction of trails on that side easier. The first trail, therefore, that was made into Yosemite, was of course made down over the south lip. The only trail entering the Tuolumne Yosemite descends the south lip, and so also does the only trail leading into the King's River Yosemite. A large majority of deer and bear and Indian trails likewise descend the south lips of Yosemites. So extensively are the movements of men and animals controlled by the previous movements of certain snow-crystals combined as glaciers. Fig. i. The direction pursued by the Yosemite trunk, after escaping from the valley, is unmistakably indicated by its immense lateral moraines extending from its lips in a west-south-westerly direction. -The right moraine was disturbed by the large tributary of Cascade Creek, and is extremely complicated in structure. The left is simple until it comes under the influence of tributaries from the south-east, and both are further obscured by forests which flourish upon their mixed soil, and by the washing of rains and melting snows, and the weathering of their bowlders, making a smooth, sandy, unmoraine-like surface. It is, therefore, the less to be wondered at that the nature of these moraines, which represent so important a part of the chips hewn from the valley in the course of its formation, should not have been sooner recognized. Similarly situated moraines extend from the lips of eve?y Yosemite wherever the ground admits of their deposition and retention. In Hetch-Hetchy and ottrer smaller and : younger Yosemites of the upper Merced, the ascending stria which measure the angle of ascent made by the bottom of their glaciers in their outflow are still clearly visible. Fig, I is the horizontal section of the end on a Yosemite valley, showing the ordinary boat-shaped edge, and lateral moraines (.M M) extending from the lips. The moraines and arrows indicate the course pursued by the outflowing ice. Fig. 2 represents the right lip of./ Yosemite, situated on the upper Merced below the confluence of Cathedral tributary. The whole lip is polished and striated. The arrows indicate the direction of the stria, which measure the an- gkrH)f ascent made by the outflowing ice. In the presentation of these studies, we have proceeded thus far with the assumption that all the valleys of the region are valleys of erosion, and that glaciers were the principal eroding agents; because the intelligible discussion of these propositions requires some knowledge of the physiognomy and general configuration of the region, as well as of the history of its ancient glaciers. Our space is here available only for very brief outlines of a portion of the argument, which will be gradually developed in subsequent articles. i That fossils were created as they occur in the rocks, is an ancient doctrine, /now so little believed that geologists are \ spared the pains of proving that nature ever deals in fragmentary creations of (-.-; ,,; I8/4-] STUDIES IN THE SIERRA. 75 Fig. 2. any sort. . All of our valleys are clearly fragmentary in some degree. Fig. 3 is a section across Yosemite Valley from Indian Cafion, which displays the stumps of slabs and columns of which the granite is here composed. Now, the complements of these broken rocks must have occupied all, or part, or more than all of the two portions of the valley, A C D and B E F. The bottom, A B, ing up and translation of rocks which. occupied its place; or, in other words, by erosion. Fig. 4 is a section across the lower portion of the valley of Illilouette south of Mount Starr King. In this case the bottom is naked, and the dotted reconstructed portions of the huge granite folds A B C D have evidently been eroded.* Even the smoothly curved Fig. 3. is covered with drift, but we may assume that if it were laid bare we would find it made up of the ends of slabs and columns like the sides, which filled the space A C E B; because in all valleys where the bottom is naked, the broken stumps do appear, showing that this valley was not formed by a fold in the mountain surface, or by a splitting asunder, or by subsidence, but by a break- trough of two rock-waves which afford sections like Fig. 5 can not be regarded as a valley originating in a fold of the surface, for we have shown in the first paper of this series that domes or extended waves, with a concentric structure like A C, may exist as concretion- * Water never erodes a wide U-shaped valley in granite, but always a narrow gorge like E F, in Fig. 4. 6$76 STUDIES IN THE SIERRA. [July, ary or crystalline masses beneath the surface of granite possessing an entirely different structure or no determinate structure whatever, as in B. The chief valley - eroding agents are water and ice. Each has been vaguely considered the more influential by different observers, although the phenomena to which they give rise are immensely different. These workmen are known by their chips, and only glacier chips form moraines which correspond in kind and quantity to the size of the valleys and condition of their surfaces. Also, their structure unfolds the secret of their origin. The constant and inseparable follow it down, we find that after trending steadily about two miles it makes a bend of a few degrees to the left (A, Fig. 6). Looking for the cause, we perceive a depression on the opposite or right wall; ascending to it, we find the depression to be the mouth of a tributary valley which leads to a crater-shaped ice-fountain (B) which gave rise to the tributary glacier that, in thrusting itself into the valley trunk, caused the bend we are studying. After maintaining the new trend thus acquired for a distance of about a mile and a half, the huge valley swerves lithely to the right, at C. Looking for the cause, we find Fig. relations of trend, size, and form which these Sierra valleys sustain to the ice- fountains in which they all head, as well as their grooved and broken sides, proclaim the eroding force to be ice. We have shown in the second paper that the trend of Yosemite valleys is always a direct resultant of the forces of their ancient glaciers, modified .by obvious peculiarities of physical structure of their rocks. The same is true of all valleys in this region. We give one example, the upper Tuolumne Valley, which is about eight miles long, and from 2,000 to 3,000 feet deep, and trends in a generally northerly direction. If we go to its head on the base of Mount Lyell, and another tributary ice-grooved valley coming in on the left, which like the first conducts back to an ice-womb (D) which gave birth to a glacier that in uniting with the trunk pushed it aside as far as its force, modified by the direction, smoothness, and declivity of its channel, enabled it to do. Below this, the noble valley is again pushed round in a curve to the left by a series of small tributaries which, of course, enter on the right, and with each change in trend there is always a corresponding change in width, or depth, or in both. No valley changes its direction withotit becoming larger. On nearing the Big Meadows it is swept entirely round to 1874-3 STUDIES IN THE SIERRA. 77 Fig. 5. the west by huge glaciers, represented by the large arrows, which descended from the flanks of Mounts Dana, Gibbs, Ord, and others to the south. For thirty miles farther, we find everywhere displayed .the same delicate yielding to glacial law, showing that, throughout the whole period of its formation, the huge granite valley was lithe as a serpent, and winced tenderly to the touch of every tributary. So simple and sublime is the dynamics of the ancient glaciers. Every valley in the region gives understandable evidence of having been equally obedient and sensitive to glacial force, and to no other./,The erosive energy of ice is almost universally under rated, because we know so little about , it. Water is our constant companion, but we can not dwell with ice. Water is far more human than ice, and also far more outspoken. If glaciers, like roaring torrents, were endowed with voices commensurate with their strength, we would be slow to question any ascription of power that has yet been bestowed upon them. With reference to size, we have seen that the greater the ice- fountains the greater the resulting valleys; but no such direct and simple proportion exists between areas drained by water streams and the valleys in which they flow. Thus, the basin of Tenaya is not one-fourth the size of the South Lyell, although its canon is much \ Fig. 6. — Illustrating Bend of Upper Tuolumne Valley. 78 STUDIES IN THE SIERRA. [July, larger. Indeed, many canons have no streams at all, whose topographical circumstances are also such as demonstrate the impossibility of their ever having had any. This state of things could not exist if the water streams which succeeded the glaciers could follow in their tracks, but the mode and extent of the compliance which glaciers yield to the topography of a mountain side, is very different from that yielded by water streams; both follow the lines of greatest declivity, but the former in a far more general way. Thus, the greater portion of the ice-current which eroded Tenaya Canon flowed over the divide from the Tuolumne region, making an ascent of over 500 feet. Water streams, of course, could not follow; hence the dry channels, and the disparity, to which we have called attention, between Tenaya Cation and its basin. Anyone who has attentively observed the habits and gestures of the upper Sierra streams, could not fail to perceive that they are young, and but little acquainted with the mountains rushing wildly down steep inclines, whirling in pools, sleeping in lakes, often halting with an embarrassed air and turning back, groping their way as best they can, moving most lightly just where the glaciers bore down most heavily. With glaciers as a key the secrets of every valley are unlocked. Streams of ice explain all the phenomena; streams of water do not explain any; neither do subsidences, fissures, or pressure plications. We have shown in the previous paper that post-glacial streams have not eroded the 500,000// part of the upper Merced canons. The deepest water gorges with which we are acquainted are between the upper and lower Yosemite falls, and in the Tenaya Canon about four miles above Mirror Lake. These are from twenty to a hundred feet deep, and are .easily distinguished from ice-eroded gorges by their narrowness and the ruggedness o https://scholarlycommons.pacific.edu/jmb/1081/thumbnail.jpg