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rich deposits were found in the gravel bars and along the margins of those streams. Two or three parties remained in their camps over winter, but the most of the adventurers returned to the valleys or to San Francisco in the fall. The next season, when the news of the discoveries brought a rush of gold-seekers from the eastern States, the lower portion of the county, and as far up as Nevada City, was explored by prospectors. One or two companies of overland immigrants that crossed the mountains by the Truckee route stopped near Rough and Ready and remained there during the winter of 1849–50. Another company of immigrants stopped in Grass Valley, and others who had found rich claims, including two or three families, spent the winter in the basin of Nevada. Mining, which commenced along the running streams, was gradually extended to the dry gulches and flats, and thence into the hills, thus greatly enlarging the known mining area.

Enough prospecting had been done in the summer and fall of 1849 to prove the surface diggings to be incredibly rich, individuals in some cases having taken sulphurets are arranged very distinctly in bands or zones, parallel to the walls, forming ‘ribbon quartz.' This is especially distinct in the Norambagua, where, as before mentioned, the sulphurets are arsenical, and the gold very finely disseminated.

“The average tenor of the gold in the Grass Valley veins is believed to be considerably in excess of what is found in most other portions of California. In Allison Ranch, Massachusetts Hill, Rocky Bar, Ophir Hill, and Eureka, this average has probably reached $50 to the top. In many other mines it has been considerably less, but, on the whole, $30 may not be far from the general average tenor of the whole district, meaning, of course, the amount actually saved by milling operations.

“The loss of gold is very various, but is probably nearly always greater than owners are willing to confess, if indeed they know, which is doubtful. It is certain, in one well-known mine, my own samples of quartz sands, and sulphurets from pans,' assayed respectively $23 and $57 per ton—a result which was later confirmed by the researches of another very competent mining engineer, quite independently. In other cases, as at Eureka and Norambagua, my own researches show the loss in the tailings to be very small, not exceeding $7 to the ton in the latter, and less than that in the former.

“The gold in many of the Grass Valley mines is very easily worked, being clean, angular, and not very small, hence it is readily entangled in the fibre of blankets, together with a con. siderable portion of sulphurets, naturally leading to the method most commonly in use in Grass valley for treatment of the gold ores."

The same authority refers as follows to the Grass Valley method of amalgamation:

“What may properly be called the 'Grass Valley mode,' consists in the use of heary stamps, 700 or 1,000 pounds, crushing usually two tons, sometimes two and a half tous of ore each in 24 hours through screens not exceeding No. 6, rarely so fine. Amalgamating in battery and copper aprons are usually united. In some mills mercurial rifles are placed in front of the discharge, but more commonly the wbole body of crushed stuff is led at once over blankets, which are washed out every few minutes into tanks, where the free gold and sulphurets are allowed to collect preparatory to being passed through the 'Attwood amalgamators.' These simple machines are designed to bring the gold into thorough contact with mercury contained in little vats, sunk in the surface of an inclined table, over which the stuff is fed to the vats in a regulated manner by a stream of water, while iron blades slowly revolve in the vats to cause a mixture of the sands and quicksilver. By this apparatus, at the Eureka mill, 90 per cent. of all the gold is obtained which is saved from the ore. Beyond the amalgamators the sands are carried over amalgamatic copper sluices, and are put through various ore-saving processes, with a view especially to concen. trating the sulphurets. These processes vary much in different mines. In some mills, especially the Ophir, much more elaborate mechanical apparatus has lately been introduced, with what results still remains to be seen. It is certain that if the method of treatment just sketched seems imperfect, (as it undoubtedly is,) it is the method which has hitherto yielded the large returns of gold for which Grass valley has obtained its well-deserved renown. As the development of the district goes forwar cases will occur of veins containing gold in state of very fine division, to which other methods of treatment must be applied. Such examples indeed already exist, and the problems which they offer will be met by the use of other systems of amalgamation, or by suitable modifications of the existing system.

“ VALUE OF THE SULPHURETS.—The sulphurets occurring in the Grass Vålley district are usually rich in gold—some of them remarkably so. In quantity they probably do not on an average amount to over one per cent of the mass of the ores, although in certain mines they are found more abundantly. For a long time there was no better inode known of treating them than the wasteful one of grinding them in pans and amalgamaling. In this way rarely was 60 per cent. of the gold tenor saved. After many abortive efforts, at length complete success has been met with in the use of Plattner's chlorination process. Mr. Deetken, out thousands of dollars in a few days, and the fame of the mines reaching other parts of the State, the hills and ravines of the county were overrun with eager prospectors in the spring and summer of 1850. During that season settlements were made and mining commenced in every part of the county, except what is now Meadow Lake township, while the towns of Nevada, Grass Valley, and Rough and Ready each became the centre of a large mining population. No definite estimate can be made of the gold product of the county in 1850; but it must have been large, for there were not less than four or five thousand men engaged in the mines. The claims were extraordinarily rich, and a considerable proportion of the miners returned to their former homes with what they considered snng fortunes, of from $5,000 to $10,000 cach, as the result of their summer's work. Never were fortunes more easily made by the unskilled laborer.

In the spring of 1851 the legislature passed an act for the organization of the county, the territory baving previously been comprised within the limits of now connected with the reduction works of the Eureka mine, is entitled to the credit of having overcome the difficulties which formerly prevented the successful use of this process in Grass Valley, a more detailed description of which will be found in our notice of the Eureka mine."

In reference to the length and depth of productive oro ground, the following remarks, by Professor Silliman, are interesting:

“Of the length of the productive portion of quartz veins and the depth at which they commence to become productive, Grass Valley offers some instructive examples:

"The North star vein, on Weimar Hill, has been proved productive on a stretch of about 1,000 feet, while the tenor of gold bas gradually increased with the depth, from an average of $20 in the upper levels to nearly double that in the lower levels. The limits named are rather those of exploration than the known extent of the productive ore. In the vein on Massachusetts and Gold Hills, on the contrary, the distribution of the ‘pay' has been found much more capricious, being at times extremely rich, and again, with no apparent reason, yielding scarcely the cost of milling. The Eureka mine offers the most remarkable example, however, of a steady increase from a nou-paying tenor of gold near the outcrop to one of uncommon productiveness. An opinion has found advocates, and has been perhaps generally accepted by most writers on the subject of gold-bearing quartz veins, that they were ricbest near surface and in depth became gradually poorer. There is nothing in the nature of the case, as it seems to me, to justify such a generalization more than there is to sustain an opposite opinion. _If we accept facts as a guide, we find in California that the deepest mines, for example, Hayward's Eureka, in Amador, 1,200 feet; North Star, 750 feet on tho slope; Princeton, in Mariposa county, 800 feet; Eureka, (Grass Valley,) 400 feet; Allison Ranch, 525 feet, &c., as a rule have had an increasing tonor of gold. If the Allison Ranch, the Princeton mine, and some others appear to be exceptions, tho answer is, we may reasonably expect the same variations of productiveness in depth which are known to exist in linear extent. The Princeton, after an excellent run of good ore, became suddenly poor, at a depth of over 600 feet, in 1865; but I am informed by Mr. Hall, the present superintendent, that the good ore came in again in a short distance. Mr. Laur, the French engineer, whoso papers of California mines is often quoted, eites the Allison Ranch mine in evidence of the theory of a decreasing tenor of gold in depth, but it is in proof that since the date of Mr. Laur's visit (1862-3) this mine has been at work on ores which have yielded over $100 value, its present suspended activity being due to causes quito unconnected with the intrinsic value of the mine. "The rich chimneys' or productive zones of ore ground are known to be of various extent in quartz veins, from a few feet to many hundreds of feet, and it is impossible to assign any valid reason why we may not expect the same changes in a vertical direction which we find in a horizontal. As the ore-bearing ground or shoots of ore have in many, if not in most cases, a well-determined pitch off the vertical, it is self-evident that a vertical shaft or incline at right angles to the veins must, in descending, pass out of the rich into the poor ground, at certain intervals, and it is perhaps due to an ignorance of this fact that mivers have abandoned sinking because they found the 'pay' suddenly cease in deptb, when a short distance more would probably bring them into another zone of good ore. rience of every gold-mining district offers examples in illustration of these remarks.. 'In quartz veins containing a considerable amount of sulphurets, it is evident that the outcroppings should offer much better returns to mining industry than will follow after the line of atmospheric decomposition has been passed, because above this lino nature has set free the gold formerly entangled in the sulphurets, leaving it available for the common modes of treatment, with the added advantage oftentimes that the particles of free gold formerly distributed through a considerable section of the rein, are fouod concentrated in a limited amount of ore. It is easy to reach the conclusion in such cases that the tenor of gold in the vein is less.in depth, after the real average tenor is reached, while in fact it is neither greater nor less ;but the metal is no longer available by common methods of treatment.

The expe

Yuba. Nevada City, then the principal town and near the centre of population, was made the county seat, where it has ever since remained. The county is divided into nine townships for local government, viz: Nevada, Grass Valley, Rough and Ready, Bridgeport, Bloomfield, Eureka, Washington, Little York, and Meadow Lake. Rough and Ready comprises the foot-hills extending across the western end of the county, from the Yuba to Bear river; Meadow Lake includes the summit extending across tho eastern end; Bridgeport, Bloomfield and Eureka lie between the middle and south Yuba on the north ; Little York is on the south, mostly lying between Bear river and Greenhorn creek; and between Rough and Ready and Meadow Lake are the townships of Grass Valley, Nevada and Washington, occupying the central position.

Of the carly settlers but few remained permanently in the county, by far the larger proportion returning to the east, or taking up their permanent abode in other parts of California. But their places were filled by other adventurers, and the population gradually assumed a permanent character, and now numbers not far from 20,000 souls, of whom about one-third are adult males. The inhabitants derive their support either directly or indirectly from the mines, on the prosperity of which depend all other branches of business.

PLACER MINING.–Placer mining properly signifies the working of the shallow deposits; but in California the term “placer" is usually applied to the deep deposits as well as the shallow diggings-hydraulic and cement mining being only branches of placer mining--and all except the quartz lodes being designated as placer mining.

The placer mines of Nevada county have been worked steadily since 1849, and have yielded an amount of treasure that, could the figures be procured, would stagger belief. The rich pockets along the margins of the streams, and the shallow diggings and ravines that required no capital and but little preliminary labor to mine successfully, have been mostly worked out, and capital and skill are now indispensable to success, yet there is but little diminution in the yield. As claims are worked out in one place new ones are opened in other localities, and although failure in any given enterprise is about as likely as success, yet the prospect of big strikes, and the hope of acquiring a fortune or a competency by one or two years of well-directed labor, are incentives that cannot fail to enlist the skill of the most energetic of the mining population.

At first, mining was confined to the gravel bars and beds of the running streams, and as these were partially exhausted, it gradually extended to the dry ravines, flats and hillsides adjacent. The rocker was the principal machine used for washing the auriferous sands and separating the gold from the lighter particles. It had been brought into use in the summer of 1848, during the first season of mining in California, though much of the gold obtained that season was separated by the Mexican method of washing the sand in wooden bowls. Sheet-iron pans are now used by the American miners for prospecting and other purposes, in place of the wooden bowls of the Mexicans. The rocker was superseded by the long-tom, by means of which a larger amount of earth and gravel could be washed; and the long-tom in its turn gavo place to the sluice. This was a most important improvement, and enabled miners to work many claims that would not pay with the rocker and long-tom.*

Professor Silliman, in a report on the property of the Eureka Ditch Company, says of the sources to which the gold in California is referable:

“The original source from whence all the gold of California has been derived is undoubtedly the veins of gold-bearing, qnartz which occur so abundantly in all the slates and metamorphic rock of the western slopes of the Sierras within the areas known as the gold regions. But this original or great source of the precious metal is historically secondary to the shallow and decp digging or placers, in the former of which gold was first discovered, and which during the early years of California history furnished nearly the whole of the metal sent into commerce. That the placers were derived from the degredation or breaking up of the auris. erous veins and the distribution of the detritus thus formed by the agency of running water

Ditches at length were constructed to bring the water over the hills, and as the miners were compelled to leave the flats and ravines and take to the deeper diggings, the process of shovelling the earth into the sluices became unprofitable, and the practice of ground-sluicing came into use. By this process the surfacesoil, being loosened up or thrown into a trench cut in the bed rock, was washed away by a stream of water, leaving only the heavy gravel at the bottom to bo shovelled into the sluices. Ground-sluicing was carried on extensively in this

and ice does not admit of a question. It appears, also, to be pretty conclusively proved that the gold-bearing gravel is of two distinct epochs, both geologically very modern, but the later period distinctly separated in time from the earlier, and its materials derived chiefly from the breaking up and redistribution of the older or deep placers. These appear to be distinctly referable to a river system different from that which now exists, flowing at a higher level, or over a less elevated continental mass, and with more power, but generally in the direction of the main valleys of the present system. It was pretty early discovered that very exten. sive and valuable deposits of auriferous gravel lay at levels far above the present course of the streams, and that to wash these deposits required the adoption of new methods adapted to meet the case. Hence came the so-called hydraulic process, which, although iu use now for more than ten years, has yet made barely more than a commencement upon the great mass of deep-lying auriferous shingle which remains to be treated by this method of gold washing

"Finally comes the era of quartz mining in depth, the successful prosecution of wbich demanded more skill and capital, as well as cheaper labor and better machinery, than the early days of California furnished. In this man undertakes to do for himself by the use of his own skill what in an earlier age nature had done for him on a grand scale, in breaking up the matrix of the precious metal, commencing at the fountain head of the stream of gold.

*"I propose at present to consider with some detail the second of the great sources of gold productions, viz: deep-lying placers. The character of these deposits is well illustrated by a description of the ground between the south and middle forks of the Yuba river, in Nevada county, where this description of gold deposit is well exposed in consequence of the consid, erable amount of mining work which has been performed there, the whole of this ground being controlled by the waters of the Middle Yuba Canal Company and of the Eureka Lake Water Company.

"The Deep PLACERS OF THE YUBA.—The Yuba is an affluent of the Feather river, which it joins at Marysville on its way to its junction with the Sacramento. The south and middle forks of the Yuba river unite with the North Yuba, the course of wbich is nearly at right angles to these two branches, whose mean course is west about 13° south, (magnetic,) the Feather river running about north and south.

"The ridge of land embraced between the south and middle forks of the Yuba is from six to eight miles in width, and to the limits of the auriferous gravel, as thus far explored, about 30 miles, forming an area of about 200 square miles. The elevation of this ridge above the sea is, at its western extremity, near French Corral, about 1,500 feet, from whence it gradually rises into the high Sierras, the Yuba Gap Pass being 4,570 feet above the sea, and the Downieville Buttes about 8,840 feet. This Mesopotamia is cut up by ravinos descending from a central axis both ways into the valleys of the two rivers forming gulches' with steep sides, often beautifully wooded. The more elevated portions of the land are covered by a heavy bed of volcanic ashes and breccia, which evidently at an earlier day formed a continuous sheet over not only the tongue of land under consideration, but over the adjacent region, as is conspicuously seen in the sections afforded by the various rivers This inass of volcanic ashes contains numerous angular fragments of cellular lava, trachyte, basalt, porphyry, and volcanic mineral aggregates quite foreign to the general geology of the country. Its thick: ness varies with the topography and drainage of the surface, but it forms the summits of all the bills above a certain horizon, and in places reaches an elevation of from 2,000 to 3,000 feet above the level of the rivers. Below Columbia the denudation of the surface has removed the volcanic matter, leaving the auriferous gravel exposed as the upper surface. This volcanic deposit receives from the miners the general name of .cement,' u terin it well deserves from its compact and tenacious character, much resembling pozzolana or Romau cement.

"The auriferous gravel varies in thickness from 80 to 100 feet, where it has been exposed to denudation, to 250 feet or more where it is protected from such action. Probably 120 feet is not an over-statement for its average thickness in the marginal portions, where it has been exposed by working the deep diggings or hydraulic claims. This vast gravel bed is composed of rounded masses of quartz, greenstone, and all the metamorphic rocks which are found in the high Sierras.

"It is often locally stratified, but I could find no evidence of any continuity in its beddings. The lower portions are composed of larger boulders than the upper as a general rule, but this does not exclude the occasional presence of huge boulders in the central and upper portions. In a fresh fracture of the whole thickness of these deposits, such as may be seen daily in the claims,' which are being actively worked, a striking contrast of color is seen between the country in 1851 and 1852, the use of the sluice proper at that time beffig well understood, and having in a great measure superceded other methods. With most of the mining improvements there were no especial inventions, but the different appliances came into use gradually as they were needed by the changing character of mining, and may be considered as the result of the combined skill and ingenuity of the mining population. William Elwell put up and used the first sluice at Nevada City, in February or March, 1850, but he does not claim it as

lower and upper portions of the gravel mass, consequent on the percolation of atmospheric waters and air, oxidizing the iron resulting from the decomposition of pyrites, and staining the gravel of a lively red and yellow color in waving lines and bands, contrasting boldly with the blue color of the unoxidized portions. A close examination of the blue colored portion of the gravel shows it to be highly impregnated with sulphuret of iron, (iron pyrites) forming, in fact, the chief cementing material which holds the pebbles in a mass as firm as couglomerate, requiring the force of gunpowder to break it up.

“In the upper portions of these beds are frequent isolated patches, often of considerable extent, composed of fine sand, clearly showing water lines, curved, sloping, or horizontal, but never for any distance regular, and in theso portions occur frequently large quantities of lignite, or fossil wood, little changed from its original condition, but blackened to the color of coal and flat with pressure. Ainong these remains are logs similar in appearance to the Manzanita, now growing abundantly on the hills of auriferous gravel. Some of these, which I measured, were 15 to 18 inches in diameter, and 10 to 15 feet in length. Occasionally the mass of this ancient driftwood accumulated in these eddies of the current, where they were deposited with the fine sands, amount almost to a continuous bed of lignite.

i. Wedge-shaped and lenticular masses of tough yellow and whitish clay also occur in the ancient drift, replacing the gravel and aftording, by their resisting power, a great impedsment to the operations of mining.

“The ‘slacking down,' or disintegration which a few months' exposure of the hard gravel 'cement produces, is due mainly, if not entirely, to the decomposition of the associated pyrites before noted. It is remarkable how large a part of the smoothed and beautifully rounded stones, even those of large size, undergo a similar slacking by atmospberic action, even in a very brief period of time, rendering it almost impossible to preserve specimens of the gravelly concrete unless they are protected by varnish. The most unsielding of the cen.ent' masses are sometimes left over one season by the miners, exposed to the air and frosts, to secure the benefits of this disintegration, without which but little of the contained gold can be obtained.

“The gold is disseminated throughout the entire mass of this great gravel deposit, not uniformly in value, but always in greater quantity near its base or on the bed rock. The upper half of the deposit is found to be always less in value than the lower part, sometimes so poor that it would be unprofitable working by itself, but inasmuch as there is no practicable mode of working the under stratum, without first moving the upper portion, in practice the whole is worked.

"The gold rarely occurs in large masses in this ancient gravel. Often on the polished and very smooth surfaces of the bed rock' and of the superincumbent masses of gravel when fres bly raised from their long resting place, the scales of brilliant yellow metal are beautifully conspicuous. These are frequently inlaid so firmly upon the hard granite floor of the ancient river or glacier as to resemble hard stone mosaics. In fact the whole surface of the bed rock requires to be worked over by the pick to secure the gold entangled in its surface, to a depth, when soft, (as of mica or chloritic slate or gneiss, ) of several inches.

“The bed rock, as it is significantly termed by the miners, shows everywhere, when freshly exposed, the most conspicuous evidence of aqueous or glacial action. The course and direction of the motion wbich bas left its traces everywhere is plainly discernable.

“The bed rock' varies of course in different portions of the area now under consideration, being either granite, gneiss, greenstone, or shale. In the granite are observed numerous minute quartz veins pursuing a course parallel to each other olten for hundreds of feet without interruption.

. In the · American claim,' at San Juan, the granite is succeeded on the west by a large jointed blue siliceous shale of the same strike with the main joints of the granite. This latter rock is covered by numerous very large boulders of metamorphic conglomerate, of which do traces are seen in place.

"The course of the ancient current, where I had an opportunity of measuring it, appears to have been about 20° to 25° west of north, (magnetic,) which it will be observed is nearly at right angles to the mean course of the middle and south forks of the Yuba river ; but it is not far from parallelism with the axis of the Sacramento river valley, or of the great valley between the coast range and the Sierra Nevada. I bave noted the same general direction of the scratches elsewhere in the great gold region, but additional observatious are required to justify any comprehensive generalization. This much appears clearly shown, however, by the present state of our knowledge on this subject, viz: that the spread of the ancient gold

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