Geological Survey Bulletin 612 Guidebook of the Western United States: Part B

SHEET No. 23. (click on image for an enlargement in a new window)

For about 2 miles from the summit the route follows an upland meadow, undoubtedly of glacial origin, the lower end of which is now submerged in a reservoir called Lake Van Norden, after a family of eastern capitalists who have taken a prominent part in the water-storage, water-supply, and hydroelectric power developments that have been so largely extended in the Sierra during the last few years. The mountain streams thus utilized supply light and power throughout much of California and Nevada.¹

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¹There are in California about 75 developed hydroelectric power plants, most of which, including the largest, are in the Sierra. Along the route of the Southern Pacific the principal developments are those of the Pacific Gas & Electric Co., which consist of a system of storage reservoirs, conduits, and power houses for the utilization of the flow of Yuba and Bear rivers. Most of the structures visible from the railroad, as at Lake Van Norden and in the vicinity of Colfax, have been built in connection with the recently completed Drum plant, which has an ultimate capacity of 40,000 kilowatts, or 53,600 horsepower. The further utilization of the power of Bear River will involve the construction of five additional power plants extending from Lake Spalding to Newcastle, the total power capacity of the completed system to be 160,000 horsepower.

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Below Soda Springs (see sheet 23, p. 214) the railroad follows the south side of the upper valley of South Fork of Yuba River, a typical glacially scoured valley, its broad and smoothly rounded bottom worn down to bare granite. Along the sides of the valley is scattered more or less morainal débris.

An especially noticeable feature of the western slope of the Sierra Nevada is the general evenness of its sky line. In any extensive view it is not difficult to overlook the deep canyons and imagine oneself looking over a great forested plain sloping gently westward. The ridges between the canyons are in fact remnants of a former surface of low relief. By the elevation and westward tilting of this surface the Sierra Nevada was formed.

The rocks near the summit are principally granite (or granodiorite),¹ lavas (andesite, rhyolite, and basalt), tuffs, and breccias. The volcanic rocks generally cap the ridges, the canyons being cut through them into granite or into sedimentary rocks which have been invaded by the granite. In general, throughout the western slope of the Sierra Nevada, the lavas, the associated gold-bearing gravels, and the other Tertiary rocks lie nearly horizontal on the worn surface or eroded edges of a much older tilted set of rocks. These older rocks comprise altered sediments, such as slates and schists, altered lavas and tuffs, in part rendered slaty or schistose by pressure, and intruded igneous masses. The various sedimentary formations are not readily distinguishable from one another from the train. The most widespread and characteristic are the Calaveras formation, of Carboniferous age, and the Mariposa slate, of Jurassic age. Both consist chiefly of slaty rocks, although the Calaveras is less uniform than the Mariposa and contains some limestone. The dip of the older rocks varies, especially near intrusive masses, but in general it is 60° to 70° E.

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¹The granodiorite of the Sierra Nevada is an enormous mass of intrusive rock only partly bared by erosion. Such a mass that extends to unknown depth is called by geologists a batholith. The batholith of the Sierra Nevada is merely one member of a chain that comprises many such masses, which extend along the western coast of North America. These immense bodies of igneous rock were intruded in late Jurassic or Cretaceous time and may all be connected at great depth.

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Near Cisco the older sedimentary formations of the Sierra begin to take the place of the granite and volcanic rocks. North of the railroad, on the summit of a high ridge known as Signal Peak, the railroad company maintains a lookout station, from which a watch is kept for fires in the snowsheds, many miles of which are in view from this one point. The ridge on which the signal station is situated is composed of metamorphosed slates (Sailor Canyon formation) of Triassic age, like those that occur at Cisco. The brown talus from these slates is in decided contrast with the white granite outcrops previously passed.

Cisco is an old railroad-construction camp, now a small settlement for the railroad employees. Here also is a summer hotel and camp. In the valley of the South Fork of the Yuba below the railroad, on the right, is a favorite summer automobile road which crosses the Sierra and forms a section of the recently named Lincoln Highway.

There are openings in the snowsheds here and there at bridges and at places where one part of the shed is made to telescope into another, being mounted on wheels for that purpose. These telescoping sections are rolled back in summer, as a precaution against the spread of fires. Crystal Lake (elevation 5,758 feet), Yuba Pass (5,614 feet), and Smart (5,351 feet) are unimportant stations in the snowsheds. The block-signal system in use on this part of the road is interesting, and an account of it may be obtained by conversing with those who are socially inclined among the railroad crews.

Just beyond Smart, near milepost 173, a glimpse forward on the right shows the South Fork of Yuba River in its now rapidly deepening valley far below. The river here turns sharply north and immediately disappears into a very narrow and deep rocky gorge. This is a striking example of what is known among physiographers as stream capture. The part of the river already passed is the former headward portion of Bear River, which now rises near this point and flows southwestward through a smooth, grassy gap, known as Emigrant Gap. Another stream on the north, the original South Fork of the Yuba, working backward at its head in the manner common to streams, cut its canyon faster and deeper than that of the ancient Bear River was cut and finally worked back into the Bear River valley and, tapping that stream, drained off its water through the narrow canyon to the north. (See fig. 17, on sheet 23, p. 214.) The present Bear River approaches within a quarter of a mile of the railroad just beyond Gold Run. The evidence of this interesting bit of ancient river history remains in view but momentarily, for the railroad plunges through a short tunnel and emerges on the opposite side of the ridge, in one of the upper tributary valleys of the American River system.

FIGURE 17.—SKETCH MAPS SHOWING CAPTURE OF UPPER PART OF BEAR RIVER BY SOUTH FORK OF YUBA RIVER. A (left), BEFORE CAPTURE. B (righ), AFTER CAPTURE. RAILROAD SHOWN TO IDENIFY LOCATION.

Emigrant Gap is the first station on the descent which suggests a surrounding agricultural or fruit-raising country. The railroad cuts expose slates and micaceous schists (Calaveras formation) which belong to the Carboniferous system. Here may be noted a change from the upper region where glaciers have scoured the rocks clean of all loose material to the lower region where a mantle of soil and disintegrated rock gives better opportunity for forest growth.

The station of Blue Canyon is situated on the timbered hillside in a deep reentrant curve of the railroad, which is here high above the North Fork of American River, near the crest of one of the characteristic flat-topped, lava-capped ridges of the mid-Sierra slope. (See Pl. XLIX, B, p. 207.) The last of the snowsheds is near at hand. Beyond them, as the road winds in and out on the mountain side, distant views bring out with great distinctness the evenness of the sky line that is significant of the smoothness of the older (early Tertiary) topographic surface by whose uplift and westward tilting in late Tertiary time the Sierra Nevada came into being as a mountain range. The depth to which the modern river canyons have been cut below this surface is an index of the amount of erosion that has been accomplished since this uplift. The old plateau surface has been deeply dissected, but it is yet far from being destroyed. The stream channels are considered as still in the "youthful" stages of their development. When they attain "maturity," perhaps thousands of years from now, the ridges between them will have been worn down to low, rounded divides, and the streams themselves, instead of roaring through rocky canyons, will glide in leisurely meanders through broad green meadows. The canyons are thus evidence of the geologic recency of the elevation of the Sierra Nevada.

Beyond Blue Canyon the train skirts a thickly wooded steep slope, above the gradually deepening canyon of Blue Creek. This part of the railroad follows closely the bottom of the lava that caps the ridge, the canyon below being cut in the slaty rocks of the Calaveras formation. The main cap rock of the ridge is andesitic tuff-breccia. Under this in places is some lighter-colored rhyolite tuff. For a while there are few distant outlooks. The hillsides are, for the most part, thickly covered with small timber and underbrush, which is evidently second growth, the original forest having been destroyed long ago by lumbering or by forest fires. At Forebay (milepost 162), which is a sidetrack and water station, there is again a partial view across the canyon to the distant level sky line. West of this are several deep cuts along the railroad, showing the character of the deposits that were formerly spread out over the old plateau surface, composed largely of fragmental volcanic materials ranging from fine tuff to coarse blocks of lava. (See Pl. XLVIII, B.) Just beyond Midas (elevation 4,142 feet, milepost 161) appears a seemingly almost sheer drop into the deep gorge of the North Fork of American River, here 2,000 feet below the track. The evenness of the ridge tops to the south, due largely to the fact that they are capped with volcanic rocks, chiefly andesite tuff-breccia, is again clearly apparent. Beyond Gorge station (elevation 3,904 feet) the railroad again skirts the 2,000-foot gorge, just above a constriction in the canyon known as Giant Gap, also as Lovers Leap. The canyon is narrow here because it cuts across a belt of altered igneous rock (amphibolite) that is harder than the slates above it. The railroad here turns northward through a little gap in the ridge into a small upland valley. The rock in the gap itself is white rhyolite tuff, but above and below the gap the railroad crosses some serpentine (an altered magnesian igneous rock) which is a part of a north-south belt of this rock that extends along this part of the Sierra slope.

PLATE XLVIII.—A (top), VIEW OF TERTIARY GOLD-GRAVEL DEPOSITS BETWEEN GOOLDRUN AND DUTCH FLAT LOOKING BACK OVER THE GOLD GRAVELS FROM GOLD RUN. Note the flume in which water is conducted, fomerly used in the washings but now employed for irrigation. B (bottom), VIEW IN A RAILROAD CUT BETWEEN FOREBAY AND MIDAS. Shows the character of the deposits laid down over the old plateau surface, which, now uplifted and tilted to the west, forms the west side of the Sierra. The cut exposes rounded stream bowlders, coarse angular blocks of lava, and layers of finer volcanic ash and sediment.

At Towle are some of the higher orchards of the Sierra, and here again, close at hand, is the Lincoln Highway. In the woods here abouts are summer camps and small hotels. In the bed of the little stream just below the railroad station on the left have lately been found some magnesite (a carbonate of magnesium) and also some asbestos. So far as known the deposits are not of sufficient extent to be of value. They occur with the serpentine, the usual association for magnesite deposits. Dark ledges of amphibolite (the same belt that occurs at Giant Gap) and of serpentine show along the railroad.

Just below Towle is a railroad cut in some of the white volcanic tuff (rhyolitic) already referred to as occurring below the andesite tuff-breccia. These volcanic deposits are mere remnants, and once extended across the areas now occupied by the canyons. The andesite tuff-breccia particularly covered enormous areas of the west slope of the Sierra before that slope was tilted by earth movements and cut into by the streams. At Alta are summer camps and a sanitarium. The surrounding country is rather thickly timbered, but there are clearings planted as orchards or cultivated in other ways.

Just beyond Alta is a sidetrack where round bowlders of white quartz, obtained from the old gold diggings a short distance away, are shipped. These bowlders are used in the furnaces of the railroad repair shops at Sacramento. They come from a placer mine which is called Nary-a-Red, referring to the absence of the usual red bowlders in these gravels. The pure white cobbles remain behind after the finer materials have been washed away by the hydraulic method of mining for gold.

Beyond a bend on the north side of the ridge the town of Dutch Flat, almost surrounded by the great pits made by hydraulic washing for gold, comes into view a short distance away from and below the railroad. The railroad station of the same name is about a mile south of the town, at a former settlement of Chinese miners that was known as Chinatown. Here the view from the railroad embraces a region that was prominent in the early mining days of California for its yield of placer gold. The gold of Dutch Flat came chiefly from the upper or bench gravels, deposited by the rivers of Tertiary time¹ and now high above the present streams. Hydraulic mining, in which the gravel is attacked by powerful jets of water, is no longer in progress near Dutch Flat, partly because the rich parts of the deposits have been worked out but chiefly because laws enacted for the protection of the agriculturists along the lower courses of the rivers prohibit the washing of silt and sand and other mining debris into the streams. The general character of these old hydraulic workings can be well seen from the railroad.

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¹The Tertiary streams that flowed down the western slope of the Sierra occupied wider valleys than the present ones and accumulated extensive deposits of gold-bearing gravels along their channels. These gravels were later covered by lavas and flows of stony mud (tuff-breccia) erupted from volcanoes near or east of the present summit. When the grade of the slope was increased by the tilting of the range in later Tertiary time the rivers cut new canyons, and many of the old channels with their lava caps now lie on the ridges. (See fig. 18.)

FIGURE 18.—Diagram showing the present relation of the Tertiary auriferous gravels to bedrock and lavas, also the position of the gravel remnants high on the ridge summits.

Of interest in connection with the Tertiary river gravels is the story of the Calaveras skull. For a time this skull attracted much attention not only from people in California, but from scientific men the world over. It was reported to have been found in 1866, near the town of Angels, Calaveras County, at a depth of 130 feet, in Tertiary gold-bearing gravels underlying Tertiary lava. The finding of a human skull embedded in such deposits was for a time believed to indicate that man had been in existence in North America very much longer than had been supposed. Strange to say, the skull is of a higher type than skulls which, although known to antedate historic times, are known also to be much younger than the Tertiary. Although Prof. J. D. Whitney, then State geologist, accepted the skull as a bit of genuine scientific evidence, it is generally believed by students of the antiquity of man that the Calaveras skull, while undoubtedly old, probably did not come from the auriferous gravels at all.

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The historically important discovery of gold in California was made in January, 1848, at John Sutter's mill on South Fork of American River near Coloma, a point only 10 or 15 miles southeast of the town of Auburn, through which the train will soon pass. From 1850 to 1853 the greatest yield was derived from the gravels, and the largest annual output for this period was more than $65,000,000, in 1852. There was some reaction in 1854, due to previous wild speculation, but a production of about $50,000,000 a year, chiefly from placer mines, was maintained up to 1861.

At first the gold was won chiefly from the gravels along the present streams. Those who first got possession of the rich bars on American, Yuba, Feather, and Stanislaus rivers and some of the smaller streams in the heart of the gold region made at times from $1,000 to $5,000 a day. In 1848 $500 to $700 a day was not unusual luck; but, on the other hand, the income of the great majority of miners was certainly far less than that of men who seriously devoted themselves to trade or even to common labor.

The gold pan, the "rocker," the "tom," the sluice, and the hydraulic "giant" or "monitor," named in the order of increasing efficiency, were the tools successively used by the miners. Into the "rocker" and the "tom" the miner shoveled gravel or "dirt," rocking the machine as he poured in water and catching the gold, often with the aid of quicksilver, on riffles set across the bottom of his box. Sometimes a stream was diverted into a flume to lay bare the gravel in its bed so that the miner could get at it. In sluicing, the gravel was shoveled into a similar but much longer box through which a stream of water was allowed to run. The hydraulic giant was employed to wash into long riffle-set sluices immense quantities of gravel, especially from the higher (Tertiary) deposits, much of which was too lean to work out by hand. Water was brought for many miles in ditches and flumes from the high Sierra and conducted under great head to a nozzle from which it was projected with tremendous force against the gravel. It was the vast quantity of refuse washed into the streams by these hydraulic operations that brought about the conflict between mining and agricultural interests, finally decided in favor of the farmers. Of late years the gold obtained from quartz veins in California has exceeded that won by placer mining.

Half a mile beyond Dutch Flat station the railroad track rests on Tertiary gold-bearing gravel, the right of way having been preserved from attack by the miners. (See Pl. XLVIII, A.) The lower part of the gravel under the railroad is said to be worth about $8 a cubic yard, and it is worthy of note that elsewhere gravels yielding only $1 or $2 a yard are now being worked with profit by tunneling or drifting. The bedrock on which the gravels at Dutch Flat rest is a dark-green, somewhat altered intrusive igneous rock (gabbro).

Just beyond the hydraulic washings is Gold Run, which like Dutch Flat was formerly a flourishing placer town. Beyond Gold Run the railroad for about 6 miles crosses a north-south belt of slate or slaty schist of Carboniferous age (Calaveras formation). These rocks are cut by dikes of dark, altered igneous rock (amphibolite). Patches of Tertiary lavas, outlying remnants of the former plateau surface, cap the highest hills along the summit of the ridge near this part of the route. On the right is Bear River, already mentioned as having lost its original upper portion, above Emigrant Gap, through capture by the South Fork of the Yuba.

Magra (elevation 2,899 feet), Cape Horn (2,656 feet), and Wirt (2,442 feet) are unimportant stations. From a point near milepost 148 can be seen placer pits at Iowa Hill and Michigan Bluff, high on the ridges across the canyon of the North Fork of American River, far away to the southeast. These places, busy mining centers of the early days, are now quiet little back-country settlements.

Just beyond Cape Horn station the train turns south along the side of a wooded ridge and suddenly, at the south end of the ridge, rounds a point known as Cape Horn. Until this year (1915) the road skirted the point at the summit of a precipice 1,500 feet above the North Fork of American River, which afforded the superb canyon view shown in Plate XLIX, A. Now the old line "around Cape Horn" has been abandoned, and railroad traffic goes through double tunnels built to eliminate what had seemed like a dangerous curve around the point. Turning back along the other side of the spur, the railroad crosses a deep ravine up which runs the narrow-gage road from Colfax to Grass Valley and Nevada City. This ravine, which opens on the North Fork of American River, is cut in slate of Jurassic age (Mariposa slate). This formation and some of the altered slaty or schistose volcanic rocks associated with it (amphibolite schist, greenstone, etc.) contain some of the principal gold-bearing quartz veins of California, including the series of veins known as the Mother Lode.¹

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¹The Mother Lode, so called because the early miners imagined it had some sort of ancestral relation to smaller lodes, extends from the vicinity of the Middle Fork of American River southward for fully 120 miles, past the towns of Placerville, Amador, Sutter Creek, Jackson, San Andreas, Angels, Jamestown, Jacksonville, Coulterville, and Mariposa. It is not, as the name implies, a single great vein, but a remarkable linear system of closely parallel and overlapping veins, some of which are many miles in length. The lode has the same general trend as the belts of slaty or schistose rock that are characteristic of the western mid-Sierra slope and follows in the main a very persistent belt of Mariposa slate, although it is not confined to that formation. In places the Mother Lode veins are in altered schistose igneous rocks (amphibolite schist or greenstone schist), in slaty rocks of the Calaveras formation, or even in serpentine.

The slaty rocks of the Mother Lode region generally dip 60° to 75° E., and most of the veins are a little less steeply inclined than the rocks in their vicinity. The veins consist chiefly of quartz carrying free gold, auriferous pyrite, and other minerals that are less constantly or less abundantly present. They were deposited in early Cretaceous time by hot waters probably given off, in part at least, by deep-lying, slowly cooling masses of granite (granodiorite).

A few of the principal mines along the Mother Lode are the Plymouth, Fremont, Bunker Hill, Original Amador, Keystone, Lincoln, Wildman-Mahoney, Eureka, Amador, Central Eureka, South Eureka, Oneida, Kennedy, Argonaut, Zeila, Gwin, Gold Cliff, Lightner, Utica, Melones, Rawhide, Dutch, App, Eagle-Shawmut, and Princeton. Not all of these are now active. The deepest mine and one of the most productive is the Kennedy, which has a vertical shaft 4,000 feet deep.

The ore of the Mother Lode is treated in stamp mills, and the gold is recovered partly by amalgamation and partly by concentration and cyanidation of the pyrite and other sulphides present. The gold quartz mines of California produce annually gold valued at from $10,000,000 to $12,000,000. The greater part of this comes from the mines along the Mother Lode.

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Beyond the ravine is Colfax, first known as Illinoistown but later renamed for Vice President Colfax. The Central Pacific Railway, being built up from the Sacramento Valley, reached this place on September 1, 1865. The Nevada County Narrow Gage Railroad runs from Colfax to the important mining districts of Grass Valley and Nevada City, where there are many lode mines that have long been productive.¹

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¹The Nevada City-Grass Valley district is second only to the much larger Mother Lode district as a source of vein gold in California, and probably nowhere else in the State has there been so great a concentration of gold in a small area. The veins occur in many kinds of rock, including granodiorite, slates of the Calaveras formation, altered volcanic rocks (greenstones, amphibolite schist etc.), and serpentine. They vary much in trend and dip, are generally rather narrow, and yield ore of higher grade than the Mother Lode veins. The veins are similar in general character to those of the Mother Lode, although they show some mineralogic differences. A famous mine of the district is the North Star, the most productive gold mine in California. From 1884 to the end of 1913 this mine has yielded gold to the value of over $15,000,000. Its main shaft, an incline, is 5,850 feet long and attains a vertical depth of 2,200 feet.

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After leaving Colfax the train passes through shallow cuts in yellow soil derived from the deep decay of the Jurassic slates. The road continues the descent along a ridge between canyons, although the traveler will hardly recognize this fact without reference to the map. The upper slopes near the railroad have been largely cleared of timber and are now covered with a dense underbrush, including manzanita,² scrub oak, and other shrubs and dwarf trees. The Jurassic rocks in some places carry a few distinctive fossils, but the numerous outcrops of slate as seen from the train do not look very different from the rocks of Carboniferous age (Calaveras) that occur east of Cape Horn.

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² The manzanita (Arctostaphylos patula) is a shrub having a smooth bark of rich leaves, and berries that resemble chocolate color, small pale-green roundish diminutive apples. It is this resemblance that gives the shrub its common name, Spanish, for little apple, by which it is known everywhere on the Pacific coast. Bears are very fond of these berries. The manzanita covers many of the hills in California with a stiff, almost impenetrable growth. Its wood is hard, and the blaze from an old gnarled root cheers many a western fireplace.

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About 2 miles below Colfax the tracks separate, the westbound route turning off to the north side of the ridge. From this point to Rocklin the two lines are in general some distance apart, although here and there they run together and at two places even cross each other. The older line, used by the westbound trains, affords the better views, as the newer, more uniformly graded track passes through deep cuts and many tunnels.

Lander (elevation 2,282 feet), New England Mills or Weimar (2,278 feet), and Applegate are all small settlements along the route. From several points in this vicinity a very fine view to the rear may be had across the level-topped upland surface which slopes up to the now distant summits of the main range near the south end of Lake Tahoe.

The route crosses obliquely the outcrops of Jurassic (Mariposa) slate and after running for a few miles near the western edge of this belt of rocks enters, near New England Mills, a belt of the Calaveras formation. This change, however, is not readily recognized from a moving train, as both formations consist largely of similar slaty and schistose rocks.

Fruit growing is obviously the principal industry of the country about Applegate, and evidences of it increase as the journey continues. The train, still following the crest of a broad ridge, passes through a country of rolling hills covered with orchards, fields of grain, and patches of timber. It is said that some of the settlements along this part of the route specialize in certain fruits. For instance, Applegate raises pears chiefly, New England Mills prunes, and so on. Snow falls occasionally here and may lie for a few hours, and there is some frost. Consequently this country is not suited to the growing of oranges and other semitropical fruits.

Clipper Gap, a little settlement on the narrow ridge followed by the railroad, is surrounded by orchards and cultivated ground. A few miles beyond it, between mileposts 128 and 127, the slates of the Calaveras formation are succeeded on the west by altered greenish igneous rocks (diabase, amphibolite, and amphibolite schist), in places slaty or schistose and decomposing in general to a reddish soil. These rocks are the record of volcanic activity in Jurassic time and perhaps also in Carboniferous time.

The westbound traveler passes along the east side of the thriving town of Auburn, the seat of Placer County, named by settlers from the city in New York. The eastbound trains go west of the town. The older part of Auburn, dating from the early mining days, is built in the valley of the small stream called Auburn Ravine, but since those days the settlement has spread over the surrounding hills and fruit growing has largely taken the place of mining. The principal fruits raised here are peaches, plums, prunes, raisin and table grapes, and olives. Many of the ranchers have a few orange trees, but these are more numerous at Newcastle, the next station, 400 feet lower, where the soil and temperature are better adapted to citrus fruits. From the suburb of Aeolia Heights, just east of the railroad, may be obtained fine views of the deep canyon of American River, similar to those seen from the train near Cape Horn (Pl. XLIX, A); and from the hills west of Auburn may be seen on a clear day the summit of Mount Diablo, on the other side of the Great Valley of Callfornia, more than 80 miles away.

PLATE XLIX.—A (top), VIEW DOWN CANYON OF NORTH FORK OF AMERICAN RIVER FROM CAPE HORN, CAL. The even sky line in the distance represents the former surface by whose elevation and western tilting the Sierra Nevada was brought into existence. Photograph furnished by Southern Pacific Co. B (bottom), BLUE CANYON, CAL. This village is near the lower limits of the snowsheds. Trees are white firs. Photograph furnished by Southern Pacific Co.

About 2 miles west of Auburn, north of the railroad, is the Ophir mining district, where gold and silver veins occur in granite (granodiorite) and greenstone (amphibolite) schist. Beyond Auburn the route continues for about 2 miles farther across amphibolite schist, which, as exposed in railroad cuts, looks like dark-colored slate and is in places rusty. The railroad winds along the south side of Dutch Ravine, keeping approximately to the general slope of the former plateau surface. Here again are remnants of the Tertiary lava cover, and at one place the railroad passes through a deep, narrow cut in the andesitic tuffs and breccias. These beds rest on granite (granodiorite), which is the prevalent rock from this vicinity down to Sacramento Valley.

Just beyond a tunnel on the westbound track is the station of Newcastle, in the center of an orchard country. Pears, peaches, and prunes are grown here, and also some oranges and lemons. Fig trees and palms may be seen near the station. Beyond Newcastle a rolling timbered lowland comes into view to the south. Granite is exposed in the cuts along the road and as bowlder-like out crops in the fields.

Penryn, like all the other stations along this part of the route, ships great quantities of fruit. Granite¹ was formerly extensively quarried here for use in railroad construction and in public buildings. A small production is still maintained.

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¹The Penryn stone is a dark biotite granite, rather uniform in color, but varying somewhat in texture in the different quarry openings. Dark blotches where the biotite crystals have segregated are avoided as far as possible in the selection of the stone. About a mile east of Penryn a gabbro, or "black granite," is quarried. This stone is used chiefly for monuments, as it takes a brilliant polish.

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At Loomis is another large granite quarry. The stone is intermediate in color and texture between that quarried at Penryn and at Rocklin. It is coarser and darker than the Rocklin granite but is finer and carries less biotite than the Penryn stone. Loomis is, however, principally a fruit-shipping point, and the fruit-packing houses may be seen near the station. It is said that fruits, especially oranges, ripen early in this section, and that injurious frosts are unknown. The soil in this locality is decomposed granite, and beyond the station bowlder-like granite ledges crop out here and there on the soil-covered plain.

Rocklin, also in the fruit belt, is the principal granite-producing locality in California, whence its name. In the vicinity of the town 20 or 25 quarries are in operation, and some of them may be seen from the railroad. The first quarry was opened in 1863, and the stone was used in construction work on the Central Pacific Railway. The stone for the State Capitol at Sacramento (Pl. L, p. 216) and for many buildings in San Francisco came from Rocklin.¹

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¹The rock is of light-gray color and of medium fine grain. Grayish quartz grains, white feldspars, black or dark-brown biotite, and silvery muscovite in small scales may be readily distinguished with the unaided eye. In composition the rock is a normal granite, but a short distance from Rocklin the country rock grades into a granodiorite.

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PLATE XL.—STATE CAPITOL AT SACRAMENTO, CAL. Photograph furnished by Southern Pacific Co.

The traveler has now practically reached the Great Valley of California. The country spreads out to the north and south in low undulations and ahead are plains as far as the eye can see.

The great gold-dredging fields of California lie along the belt of country where the Sierra slope merges into the valley plain, but none of these fields is crossed by the Overland Route. One productive district is near Folsom, about 10 miles south of Rocklin, on American River. This district produced gold to the value of $2,498,603 in 1913. The Marysville dredging district, on Yuba River about 30 miles northwest of Rocklin, produced $2,420,455 in 1913, and the Oroville district, on Feather River about 25 miles north of Marysville, $1,918,050. The gold is obtained by powerful electrically driven dredges—huge floating scows, some of them 150 feet long, provided with great buckets, linked together in an endless chain, for scooping up the gravel and with complete machinery for screening and washing the gravel and recovering the gold. Once floated in a pond the dredges dig their way through fields, vineyards, and orchards, filling in behind them with washed gravel. The gold was brought down from the slopes of the Sierra and deposited in recent geologic time by the rivers near which the dredges are working. Of late years the hard bowlders left by the dredging have been crushed and utilized as broken rock for road building. Some effort has been made also to restore the dredged ground to arable condition. Where this has been successfully accomplished in the Sacramento region vineyards and olive groves occupy areas from which gold and road metal have been mined.

At the west base of the Sierra, but not continuously exposed all along it, are beds of brown Upper Cretaceous sandstone (Chico formation) and of lighter-colored Eocene sandstone and clay, containing thin coal beds (Ione formation).² All these beds are younger than the rocks forming the mass of the Sierra and have not been squeezed or altered. They dip gently westward and are covered by gravels, silts, and muds washed into the Great Valley of California by streams. Remnants of the lavas that were poured down the Sierra slopes during Tertiary time cap some of the foothills along this part of the route. West of them all is open plain.

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²The lone formation has been described as Miocene, but recent investigations indicate that it is Eocene.

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At Roseville the main line is joined from the north by the Southern Pacific Co.'s line to Marysville, Chico, and Tehama. At Tehama this line joins the main Shasta Route of the same company, which south of Tehama lies along the west side of Sacramento Valley. Beyond Roseville is a nearly level country, practically all of which is under cultivation, chiefly in grain but partly in orchards. The scattered oak trees in this part of the valley include two species, the live oak and the valley oak. (See footnote on p. 203.)