of its natural bed; the construction of a permanent head dam; the procuring of power, which was obtained by repairing the old Miocene ditch, which required 5 miles of iron piping; also the erection of an electric plant, to enable the work to be carried on by night as well as by day, and the connection of all the different points and the ditch stations with the head offices by telephone, requiring over 40 miles of telephone wire. In the construction of the canal, a cemented rock wall was carried along the entire distance next the river, at a width of 4 feet on top and 12 feet on the bottom, reaching, in places, a height of over 20 feet from bedrock, containing over 10,000 cubic yards of masonry; in the construction of which 6,000 barrels of Gillingham cement were consumed, costing $4 68 per barrel laid down at the works, bringing the cost of the wall up to $7 50 per yard. In this work the masons employed received an average of $3 per day; blacksmiths, from $3 50 to $4; rock excavators, according to the hardness of the rock worked on, 80 cents, $1 50, and $2 per cubic yard. Two suspension bridges cross the canal, giving access to the work from the shore. One of the bridges is 80 feet long, carrying the pipe-line across that conveys the water power from the Miocene ditch; a diminishing iron pipe is made use of, receding from 32 inches in diameter to 22 inches, constructed out of No. 14 and No. 12 iron. The company have the use of 1,000 inches of water, in return for repairing and keeping the ditch in order. The permanent head dam extends from a rocky point at the foot of South Table Mountain, to a high mass of rock near the middle of the river, and from there to the opposite shore. The first 120 feet next to the west bank is occupied by the fore bay of the canal and a side dam 70 feet long providing for the waste way. The main dam is about 144 feet long, and consists of cribs of peeled pine poles from 10 to 12 inches in diameter, spiked together with wrought-iron spikes (three tons were used in the construction), and filled with the heaviest rocks that the derricks could handle, quarried out of the river banks; all surmounted by framed timbers 8x8 inches, and crowned with a shelter dam that can be raised or lowered. This latter provision is made to meet any unexpected rise in the river. It required 70,000 feet of round timbers and 6,000 cubic yards of rock in the construction, and has a height of 52 feet. The water slope is doubly planked with 2-inch boards. The upstream slope is boarded and made tight by sluicing in sand, earth, and gravel from the banks. The dam is provided with a water cushion, and everything done for the security of the work that knowledge and experience could suggest. To prevent damage to the head of the canal by the waters coming down Morris Ravine in the spring of the year, it became necessary to wingdam the mouth of that gulch. A sub-flume is built along the east bank, discharging over the end dam. Two hydraulic elevators are used, which are supplied with power from a reservoir in the adjoining hills, whose lifting power with 1,000 inches of water under a head of 480 feet amounts to 540,000 gallons an hour, discharging into the sub-flume. Two hundred cubic yards are raised by the larger elevator per hour, on a slope of 42°, to a height of 55 feet. The elevator is 20 inches in diameter, with a 44-inch nozzle. The gold found in this part of the river during the preparatory work along the rim is fine and thin, somewhat like cucumber seed, and sells for $18 50 per ounce. The accompanying contour map and photographs of the dam and canal will convey an idea of the magnitude and solidity of the work undertaken. THE GOLDEN GATE CHANNEL MINING COMPANY. This property, like the preceding, on to which it joins, is intended to work a part of the bed of the Feather River, but as the conditions are somewhat different, the channel being confined between steeper and more contracted banks, in place of a canal to carry the river, a flume has been constructed at an elevation of 90 feet above the bed of the stream, dropping it at the end of the claim into the canal of the Golden Feather Company. The head dam of this claim is situated at Long Bar, about 2 miles above Oroville, and has a total width from bank to bank of 374 feet, and a height of 52 feet. It consists of cribs filled with large-sized rocks chinked in solid with smaller gravel. In the construction 45,000 feet of round timbers were used, and 20,000 tons of rock, besides 3 tons of spikes. The flume starts on the west side of the dam, and commences with a width of 80 feet, decreasing in the following 300 feet to its normal size of 40 feet, which it retains throughout its entire length of 3,900 feet. An extension flume carries the water to the Golden Feather Channel Company's canal. In the construction of the flume, 1,250,000 feet of lumber was used, costing from $14 to $18 per thousand. The posts average 12 inches at the butt, running to 8 inches in the taper. Five stringers of 8x8-inch spruce timber held the 6x6-inch cross-ties, placed 4 feet apart. The bottom and sides are formed of 14-inch boards, the sides being 5 feet high. The mortised side posts are made of 4x6-inch stuff, held together with 4x4-inch braces. Each piece is marked and everything so arranged that in case of a sudden rise in the river, the entire flume can be removed inside of forty-eight hours. The water flows though the flume at an even grade of one inch to the rod. At extreme low water it flows 24 feet deep, with a velocity of 18 feet per second, indicating a flow of 1,440 cubic feet per second, or 72,000 miner's inches, under a 4-inch head. Last year it carried 125,000 miner's inches, being the largest amount of water ever carried by a flume. The dam raises the water to a depth of 50 feet, and backs it up for a distance of 7 miles. Powerful wheels will be used to run the pumps in getting rid of the seepage and the dead water between the head and foot dams, which is passed into a sub-flume 8 feet wide, with a grade of one quarter inch to the rod, carrying an average depth of 3 feet of water. Unlike the Golden Feather Channel Company's ground this part of the bed of the river was found to be covered by debris to a depth in places of over 40 feet, which will all have to be removed before the pay gravel in the bottom can be handled. Work will be carried on day and night with the assistance of the electric light. During the season of low water as many as five hundred men are employed in these two mines. The average depth of the pay gravel in these mines is about 4 feet. The bedrock is diabase. The average working season is estimated |