Tahoe Water Company, a distance of two and a half miles through the granite of the Sierra Nevadas, from Lake Tahoe to the North Fork of the American River.

A writer in the Commercial Herald of San Francisco thus sums up the effects of the introduction of these improved mining appliances: "It is hardly possible to overestimate the importance of these inventions in their bearing on certain of our mining industries. The great item of cost, and, what is almost equally to be dreaded, of delay, in opening up our vein-mines, old river channels, and gravel beds-the sources of our greatest and most enduring mineral wealth-have been the excavation of the tunneling necessary to reach and work them. Some of the tunnels driven to open up and drain the last two mentioned classes of deposits have cost enormous sums, requiring often from five to ten years for their completion; and, although when finished these mines are apt to prove very profitable, few men care to embark in enterprises directed to their development, with the prospect of hav ing to wait so long for returns-this, rather than the cost of these works, even when prosecuted by hand-drilling, being the deterring motive. With the introduction of these drills, lessening so much the cost, while it almost annihilates this major objection, we may look for a great extension of these several kinds of mining, increasing materially the value of such properties, and adding proportionally to the available wealth of the country."

Having given a general review of the condition and prospects of pla cer-mining, I will proceed to a description of some of the most prominent districts and the mines found therein. In the description of mines I have selected those which may be considered as representatives of their districts, with no intention to disparage the merits of equally im portant claims in the same vicinity.

THE SMARTSVILLE HYDRAULIC MINES.

These mines are situated among the foot-hills of Yuba County, near the south bank of the Yuba river, about eighteen miles east of Marysville, and are noted for the gigantic character of the engineering works constructed for their development, and the princely incomes enjoyed by their owners. The mining ground here consists of a strip of auriferous deposits two miles in length by a quarter of a mile in width, overlying an ancient channel, and having an average depth of 240 feet. The ele vation of the bed-rock above the water level of the Yuba River is about 500 feet. This river runs nearly parallel with the course of the ancient stream, from which it is less than one mile distant. The consequence is that the companies working this deposit have been compelled to run long tunnels with a slight grade, and do not possess the natural advan tages for the construction of dumps and undercurrents, which form such an important feature in saving the gold in hydraulic operations. The whole extent of this ground is now owned by six or seven compa nies, each having separate bed-rock tunnels in the course of construction and nearly completed-the most noted of which is the Blue Point Gravel Company's tunnel, the largest and most expensive undertaking of the kind in the State. It is not improbable that there is as much rich ground in the State embraced within a like area, but none which has been so systematically worked, and yielded such large returns.

Mining in this vicinity was cominenced as early as 1849 and 1850, though at that time confined to the banks of the Yuba River. Subsequent exploration revealed the existence of the gravel ridge, but after

working on it to a depth of from two to four feet a hard cement was encountered which could not be worked, by the primitive mode of mining then in vogue, with returns sufficient to pay the miners, and for a time the deposit was considered exhausted and attention again directed to the partially worked-out bars and banks of the Yuba.

In the fall of 1854 attention was again directed to the prospecting of the rich placers of Sucker Flat. Shafts were sunk on what is now known as the Blue Point Mining Company's claims to the depth of some fifty feet, passing through good pay-ground and striking rich gravel similar to that found in the bed of the Yuba River, which proved to be the gravel of an ancient river channel. Prospecting was then actively commenced in every direction. A shaft was sunk on what is now known as the Blue Gravel Company's mine, striking the same gravel as that found by the Blue Point Company. It required a large extent of ground to justify the running of a bed-rock tunnel to drain and work these deep diggings, and the Blue Gravel Company was formed by the consolidation of several small companies into a corporation which commenced a tunnel, making but little progress upon it until the present owners became interested. After some eight years of incessant toil they com pleted the tunnel in 1864, from the working of which several parties realized large fortunes, and the mine is still producing handsomely. This tunnel proved too high to work the old river channel to the bottom-there being some thirty feet of gravel below the present working level, to open which a second bed-rock tunnel, 1,500 feet in length, is now being constructed, two-thirds of which is already completed.

For the prosecution of this work the diamond drill will be used, as that invention has been tried in an experimental way, and found to accomplish all that was claimed for it, but the steam-power used was not adapted to tunnels of this size and length, on account of the excessive heat generated by the pipes, which carry the power from the mouth of the tunnel to the drills. To obviate this difficulty, the San Francisco agents of the diamond drills are constructing a machine to be run by compressed air. This machine will set on a truck about three feet wide and four feet long. It has a frame reaching to the top and sides of the tunnel on which the drills are run in such a manner that the rock or face of the tunnel can be pierced at any place, or any angle desired, without moving the truck. One or all of these drills can be used at a time. There will be a crank geared to the wheels, so that one man sitting on the machine can easily run it up to the face of the tunnel and back in a moment. This machine will cost about $10,000, and will bore holes one inch in diameter in the hard rock of the Blue Gravel Company at an average rate of an inch per minute.

A contributor of the Overland Monthly (August and September numbers, 1870,) in a series of papers descriptive of these mines, makes the following statement of the product of the Blue Gravel Company's mine from the time of opening up to May, 1870: "This mine commenced operations in 1853, and during the nine succeeding years the amount taken from it was $315,000. This was prior to and during the building of the main tunnel, and was all used for current expenses. In 1864 the tunnel was completed, and the showing becomes more favorable; for, during the forty-three months that followed, the amount was $837,000, or an average of $19,465 51 per month. The net earnings during the same time were $627,000; the cost of operating the mine being $5,000 per month, with $61,000 used for improvements. From 1868 to 1870, or about three years, the amount (given approximately) will hardly equal the former average. Taking $16,000 as the monthly product, which is

Powder blasts.-One of the characteristics of mining operations at Smartsville is the use of large quantities of powder in blasts for the purpose of breaking up the cemented banks preparatory to washing them off. Blasts of 200 or 300 kegs are of almost monthly occurrence, but blasts of such dimensions as the one exploded in December, 1870, by the Blue Point Gravel Mining Company, in which 2,000 kegs of powder were exploded, are sufficiently rare to merit a detailed description. The bank to be raised in this instance was 73 feet deep, 275 feet long, and 200 feet wide. The annexed diagram will convey some idea of the manner in which the powder was distributed:

The ring on the diagram represents the termination of the incline from the tunnel, 73 feet below the surface. From this point a main drift was run, with cross drifts as laid down in the diagram-each drift being 3 by 4 feet in dimensions. The blast was discharged by a galvanic battery, for which purpose wires were carried through the main drift-going in on one side of the crossdrifts, thence passing out through the drifts on the opposite sides. A cartridge, connected with the wire, was then placed in a keg of powder in each of the cross-drifts-there being ten points at which the powder was fired simultaneously. The heads were taken out of the kegs of powder-of which 2,000 were used in this blastequally distributed, through the drifts. The

mouth of the main drift to the first cross-drift was then firmly tamped, leav ing a large open space in the balance of the drifts, which greatly increased the explosive effects of the powder, and the blast was fired. The result was, that the entire mass of earth, comprising 150,000 cubic yards, was raised from 6 to 10 feet and thoroughly loosened. The first "fifty days' run" after this blast yielded a very large return of gold. From 100 boxes (1,200 feet of flume) at the head of the tunnel, $42,260 was taken, leaving 230 boxes of the lower end of the flume untouched.

BETWEEN THE MIDDLE AND SOUTH YUBAS.

The easterly extremity of the Smartsville deposit is found at Mooney Flat, one-half mile from the grounds of the companies above described. From this point to French Corral, on the north bank of the South Yuba, distant ten or twelve miles on an air-line, there are no surface traces of the ancient channel. It is probable that the gravel range extending

from French Corral through Birchville and Sweetland to the Middle Fork of the Yuba River, near North San Juan, is identical with the Smartsville deposit, and that between Mooney Flat and French Corral it has been broken by the South Yuba, which runs through a gorge nearly 1,600 feet lower than the bed-rock of the ancient channel at French Corral. The fact that the deposit does not make its appearance between the south bank of the South Yuba and Mooney Flat, may be accounted for by taking into consideration the denuding action of Deer Creek, once a powerful stream, which runs on about the same level as the bed-rock of the ancient channel. The eroding action of these two streams has undoubtedly broken up and scattered the ancient channel deposit between the points above named. From French Corral to Moore's Flat, a distance of nearly thirty miles, between the South and Middle Yubas, we find a series of mining towns, the most noted of which are North San Juan and North Bloomfield, the latter place being known in early days as "Humbug." The auriferous deposit is not, however, continuous, and the deposits do not belong to the same system-the lower one coming in from Camptonville and the upper one from Snow Tent-the latter being covered with volcanic matter.

French Corral. This locality has been worked from a very early period in the history of mining in Nevada County, and has proved uniformly rich. The width of the auriferous deposit is about 1,000 feet, with an average depth of 150 feet-130 feet of which is hydraulic dirt, the balance being cemented gravel of sufficient hardness to require crushing. The bed-rock is granite and slate, with narrow seams of quartz at the junction of these formations. Water is brought from Shady Creek, a distance of ten miles, through a ditch having a capacity of 2,500 inches, and which cost, with its reservoirs, at least $150,000. Water is sold at 123 cents per inch. The ditch is owned by W. M. Eddy & Co., who also conduct the most extensive mining operations in this locality. They own 1,800 feet on the channel, and use 1,000 inches of water per day, running their dirt through a tunnel 1,000 feet in length and 2,500 feet of flume. They have also a fifteen-stamp mill for crushing the cement. Two other mills are in operation here-the Empire, twenty stamps, and the Kansas Company, ten stamps. The latter company are now taking out between $400 and $500 per day. Eddy & Co.'s mill has fifteen stamps, of 650 pounds each, run by a "hurdy-gurdy" wheel 12 feet in diameter, using 75 inches of water under a fall of 146 feet. This company has been using one-eighth-inch screens, but propose to change them for screens having quarter-inch apertures. This will permit the escape of the small pebbles, and will increase the crushing capacity of the mill from eighty to one hundred tons per day. One of the companies operating here has tried this experiment with satisfactory results, having increased their crushing capacity 25 per cent. without any diminution of the product per ton. The gravel crushed in Eddy & Co.'s mill has averaged between $4 and $5 per ton, and the expense of milling and mining has not exceeded $56 per day, or 70 cents per ton, (or 16 cubic feet.) The cement is loosened by powder blasts and the mining carried on above-ground. For this purpose, powder drifts are run with single hand-drills, and fine powder used in the blast holes. Mr. Eddy estimates the advantages of this over the old system (large drills and coarse powder) at fully 30 per cent. The construction of two bed-rock tunnels is in contemplation here, each of which will be from 1,600 to 1,800 feet in length, and will debouch on the South Yuba River. On account of the many seams found in the bed-rock, the cost of running tunnels here rarely exceeds $15 per linear foot. The estimated

gold product of French Corral for 1870 is $200,000 and the same amount may be anticipated for 1871. From French Corral to Birchville, a distance of two miles, less than one thousand feet of the bed-rock has been stripped, and it is estimated that not more than one-tenth of the surface dirt has been run off.

Birchville and Sweetland.-At Birchville the Bedrock Tunnel Company have just completed a tunnel from the Middle Yuba 2,600 feet in length, at a cost of $36,000. This company do not own enough surface ground to remunerate them for this extensive work, and until the sur face ground and the tunnel are owned by one company but little work will be done at this place, though the ground is known to be rich. At Buckeye Hill, near Sweetland, the Buckeye Hill Mining Company, an English corporation, are carrying on extensive operations, with good prospects for large returns for 1871.

North San Juan.-This was formerly one of the most populous mining towns of Nevada County, but is now suffering from the stagnation incident to the exhaustion of the most accessible ground. There is yet much ground to work, but the present price for water-163 cents per inch-does not afford remuneration to small owners, and many claims are passing into the hands of the ditch company. When the claims here shall have been consolidated, extensive operations will be resumed. During the past season only four claims have used water.

The American Company's claims.—The beneficial effects of consolida tion may be illustrated by the success which has attended the operations of this company. The grounds of the American Company are located on Manzanita Hill, about one and a half miles west of the town of North San Juan. Commencing at the bluff overhanging the Middle Yuba, their claim runs 4,000 feet in a southerly direction-the general course of the channel being from north to south, and the grade of the old riverbed falling at the rate of 90 feet to the mile. The width of the pay dirt is from 300 to 450 feet, with an average depth of 175 feet from surface to bed-rock. The bed-rock is granite, and has a well-defined seam or crack running through it, from north to south, near the middle of the channel, and penetrating to unknown depths. This seam has been found 800 feet below the bed of the old channel, at a point where the main bed-rock tunnel has been commenced; and the various tunnels of the company, commencing on the hillside overhanging the Middle Yuba, have followed it, thereby diminishing the expense of running these tunnels from $40 to $15 per linear foot. The ground of this company was worked as early as 1853, but it did not pass into the hands of the present owners till 1863, when additional ground was purchased from time to time, at an expense of over $140,000, until the present extensive tract was acquired. This tract has a superficial area of about forty-two acres, and, estimating its average breadth at 450 feet, and depth at 175 feet, would give 11,597,100 cubic yards of auriferous dirt. Considerably less than one-half of this immense tract has been run off and has yielded $1,000,000, of which $400,000 has been profit. Estimating the product of the remaining ground at 28 cents per cubic yard, which is lower than the estimates of Professor Silliman or Professor Lauer for this mining region, and consistent with the past results of the working of the com pany, I am warranted in the belief that this claim will yet produce $2,000,000, of which more than one-half will in future be realized as profit. Even with the present improvements in th.s branch of mining, it is not probable that the undeveloped ground of the company can be washed off in less than sixteen years, without taking into consideration the lower grade of dirt left on the sides of the channel, or the cement