bonized or converted into charcoal, and, as the fire below burns out, the charred or carbonized wood will settle down and continually feed the fire. At the back of the chamber, E, is a hot-air chamber, F, into which the heat, gases, and flame from the chamber, E, and also steam,

when desirable, pass through the flue, g. A blast pipe, h, enters the chamber, F, at about an equal height with the flue, g, while a branchpipe, i, passes to the front and enters the chamber, E, so as to deliver its blast directly under the fire in the grate. The blasts from these pipes are regulated by dampers, j, j'. When the damper of the pipe, h, is closed, and the damper, j', opened, the blast will be delivered upon the grate, and a reducing flame produced which will pass through the flue, 9, into the chamber, F, and when the damper, j, is opened, oxygen will be supplied to the revolving cylinder, K, which contains the ore, through the chamber, F, and an oxidizing heat produced. In communication with the chamber, F, opposite the blast-pipe, h, is the revolving cylinder, K, into which the ore is fed through the hopper, L, so that as the ore meets the blast and heat from the chamber, F, it will be carried into the revolving cylinder, and there subjected to heat and roasted while passing through. In connection with the furnace, A, and revolving cylinder, K, is the dust-chamber, B. The heavy ore passes from the cylinder, K, into this chamber, and is taken away from the doors below. The light dust is carried by the current of air against the revolving perforated disks in O, one-half of which are submerged in water. These disks permit the passage of air, but the wet surfaces catch the dust, which, by the revolution, is carried under the water and washed off into the vat below, where it can be taken out when required.

The process of feeding the wood into the closed chamber, where it may be subjected to heat without air, is an important improvement, and,

as can be seen, it will descend to the fire as it is needed. The cylinder is worked by friction gearing.*

Rock-drilling machines.-This class of inventions was introduced in California in 1870, and is now extensively used in this and adjoining States and Territories. The only machines of this description in use in California are the diamond drill (Leschot's patent, as improved by Severance & Holt) and the Blatchley drill, invented by Dr. Blatchley, of San Francisco, the Burleigh drill used in the eastern States and in Colorado never having been introduced here. To the successful operation of these drills we are in a great measure indebted for the recent investment of capital in and consequent development of our great mineral resources. By the use of these machines bed-rock tunnels can be run in from one-half to one-sixth of the time required by hand-drilling, so that one of the greatest objections to this kind of mining (the great length of time required to drive a long tunnel) is obviated. All over the Pacific coast are innumerable mines that will almost pay for working by the ordinary method, which, by the use of these drills, can be made to yield a large profit. A cheap, simple, durable, and efficient rock-drill, whereby the power of fifty or oue hundred men can be concentrated in driving one drift or tunnel, has long been a desideratum, and has long exercised the ingenuity of our mechanics and miners. The system of drilling by machinery used in the construction of large tunnels, such as the Hoosac and the Mount Cenis, was not adapted to our mining tunnels, which are rarely more than 6 by 4 feet in dimensions. The great difficulty was in the application of power. Steam was tried, but the pipes conveying steam to the drills at the face of the tunnel created an unbearable heat in the tunnels, and this plan was abandoned. Compressed air was next tried, with better results, but the construction of compressors involved a great additional expense, which neutralized the utility of drilling by power. We have reason to believe that all obstacles have now been overcome by the use of water under pressure as a motive power.

The diamond drill.-A. J. Severance, after two years of constant labor and experiments in building and running the diamond drill in tunnels and open-cut rock-work, has at last brought this drill to a high state of perfection. He has been engaged in running some of our hardest bedrock tunnels, and has proved by actual demonstration that he has run the same tunnel many hundred feet with one of his improved drills at a cost of $30 per foot, the same tunnel costing by hand-labor $46 per foot, besides running twice the number of feet per month as was run by hand. By recent improvements his drills can be placed at any angle and adjusted so as to be able to bore holes in any desired direction as easily as by hand-drilling; and during the last 400 feet run in a tunnel 61 by 91, not a hole was drilled by hand-labor. Heretofore these drills have been run by compressed air, or by steam power; but recent modifications have been made by him doing away with the great cost of an air-compressor or steam-power, and in its place the application of waterpower has superseded steam or air. This has been accomplished by attaching an ordinary hurdy-gurdy wheel or a small turbine upon the *There is no feature in this furnace which can fairly be called new, taken by itself. E is an ordinary gas-generator; the introduction of air to the carbonic oxide from the generator is necessarily involved in the use of the latter; and the use of the cylinder is equally familiar. Novelty may, however, be claimed for this combination of well-known contrivances. But it is open to another objection, which concerns me more than any question of novelty. It is an arrangement for procuring a blow-pipe heat when no such heat is required, indeed, for a process (namely, that of roasting) to which such a heat is fatal.-R. W. R.

car.

back end of the car, upon the front end of which the drills are firmly secured. The drill-car is made to suit the same track as the rock-car, and when eight to twelve holes are bored the drill is disconnected by detaching the feed-hose, (rubber or canvas, three inches in diameter,) which simply connects the water-pipe to the nozzle, which plays upon the water-wheel, and is geared to the drills upon the front end of the The car is then run back to a chamber in the tunnel, the holes loaded and filled, or exploded with a battery simultaneously, thus utilizing the whole force of the powder. As many as 663 cubic feet of loose rock have been obtained by a single shot of twelve holes in a tunnel 63 by 93 feet. This new method of using water-power in the tunnel has completely satisfied the miners that the year 1871 has been a year of progression in mining, and that the day is now close at hand when their tunnels can be run much cheaper and at a great saving of time, most of the mines having already hydraulic pressure by means of ditches, affording them plenty of water. The amount of water required depends upon the head obtained. For a two-drill machine, under 300 foot head, about ten to fifteen miners' inches is sufficient; but the more head the less water is required. The water may be taken from the ditch at any distance from the drill, and conveyed down to the mouth of and up the tunnel to the drill at the face of the tunnel, and it may be conducted through a 4 or 6-inch pipe, made of No. 10 to 24 iron, according to the amount of pressure at hand. Two machines just sold to the Union and American Companies in Nevada County are being run under 300-foot pressure. Where there is no natural head of water, one can easily be created by means of Knowles's patent steam-pump, which can be placed at the mouth of the tunnel and supplied with water by means of a small reservoir, thus pumping the water up the tunnel through a pipe against the wheel, the water thus running back into the reservoir, and being pumped over and over again without exhausting the supply. A trial was made recently at the Miners' Foundery in San Francisco for the benefit of mining and scientific men. The pump used was a small-sized Knowles pump, steam-cylinder 10 inches, water-cylinder 5 inches; pressure raised upon the pump 70 pounds-equal to about 150 feet of waterhead; and two drills were run at the same time through hard granite, boring a 1 inch hole at the rate of one inch per minute. Mr. Sutro, of the Sutro tunnel, with his engineer, witnessed the workings of the drill, and at once purchased one for his tunnel, which no doubt will save at least three-fourths of the time required over hand labor. This new application has overcome all doubts and difficulties in the way; tunnels are being run which for years have been abandoned, and new ones are started.

The Diamond drill is now in use in tunnel operations at Smartsville, Yuba County; the Union Gravel Company's ground, Nevada County; the American Company's ground, North San Juan; Nevada County, Oregon City, Butte County; the Taeff and Franklin ground, Dutch Flat, Placer County, and in many other localities in perpendicular boring for prospecting purposes, or in boring for water. Some details of its operations in running tunnels will be found in this report, where operations at Smartsville, Yuba County, are described.

During the publication of this report a novel and important application of the Diamond drill has been successfully made at Saint Clair, Pennsylvania, in the sinking of deep shafts. This will be fully described in my next report; in this place I can only say that the peculiarity of the method consists in boring a large number of holes from the surface to the full depth of the proposed shaft, unless this is too great. Three

hundred feet is the depth of the holes in the shaft referred to. These are then filled up with sand. When the drilling is over the machines are removed, and blasting commences. Four feet of the sand is removed with a common sand-pump from the upper part of each hole, and one foot of clay-tamping is put in. This leaves an ordinary threefoot hole, which is blasted out, (with dualine or giant powder.) The interior holes are fired first, and afterwards those which have been bored in the corners and along the sides of the shaft. This process is repeated until the holes have been "used up," and the shaft is down to the bottom of the borings. If additional depth is desired the machines are set at work again, and a new set of deep borings is made. The sides and corners are found to be remarkably true and smooth. The drills here used are not annular, but have full convex heads in which the diamonds are set, and which are perforated to permit the passage of water. A stream, passing down through the tube used as a drill-rod, and up on the outside of this tube, keeps the hole clean and the drill-head cool. The expense and the time required for sinking a shaft are by this method both greatly reduced. The average rate of drilling has been 34 feet per day, the maximum thus far for a single machine being 67 feet in 8 hours. The shaft has been blasted out at the rate of over 25 feet per week. Mr. M. C. Bullock, engineer of the American Diamond Drill Company, 61 Liberty street, New York, is one of the patentees of the process, and Mr. Henry Pleasants is the engineer in charge of the work.

The Blatchley drill.-This drill, which was briefly noticed in my last report, is rapidly growing in favor. It has but recently been perfected, and is unlike any other rock-drill, both in principle and construction. It operates by percussion, and the blow is like that of the churn drill. It gives from three to six hundred blows per minute of as great a force as the drill-point will sustain. This is a greater degree of speed than has heretofore been obtained; consequently it drills more rapidly than it has been possible to drill before this machine was invented. It has an automatic feed, whereby the drill is fed forward just as fast as it cuts, and no faster; in hard rock, slowly; and in softer rock, more rapidly, precisely as it is required for its most efficient operations. At each blow the drill makes a part of one revolution so as to strike in a different place at each blow, as a miner turns his drill in hand-drilling. It contains only about one-fourth as many pieces as other power-drills, and does not depend for its action on any springs or pivots, liable to get out of order. It has no steam or air-engines attached to the drill with delicate parts and nice adjustments to be destroyed by the concussion and recoil of the blow. The construction is such that the connections between the drill and the driving machinery cease at the moment the blow is delivered, so that there is no recoil on the machine. On this account it can be set up in a mine on a plank, and does not require a car and heavy fastenings to hold it in place when in operation. It is estimated that a miner working at ordinary speed strikes twenty blows per minute; but this machine will strike five hundred in the same time, all of equal force, and all precisely square against the rock, thus doing the work of thirty men; and as four or five, and even more of these machines can be run in an ordinary-sized drift or tunnel, at the same time, the work of a hundred men can be done in the space where only four could work by the old method of hand-drilling. In form it is composed of two cylinders, the shorter and larger one being placed on the top of the other. In the small size, the large cylinder in which the drill moves is twenty-two inches in length and three inches in diameter;

it has flanges on the bottom by which it is secured when in operation. The other cylinder is seven inches long and five in diameter, and is secured on the top of the other at one end and parallel with it, the two being arranged somewhat like the barrels of an opera-glass. The upper cylinder revolves and communicates a reciprocating motion to the drill. The length of the whole machine, excepting the drill, is twenty-two inches, height eight, and the width five inches, excepting the flanges, which are ten inches; and the weight is seventy-six pounds. The drill is of the length required to reach the bottom of the hole, and may be of any length, from one foot to six feet or more. This small size enables it to be used in any tunnel, shaft, or place in a mine where a miner can enter, and is so arranged that it will bore a hole in any direction. It can be put in operation in a tunnel in a few minutes after a blast is exploded, and before the broken rock is removed, and while it is running the débris can be taken away. In a small space one man can operate one machine, but in a quarry where there is sufficient room he can manage several. It requires no more skill to run it than is required to operate a sewing-machine, and any miner of ordinary intelligence can learn to run it in a couple of days. It takes from onehalf to one horse-power to run it. The motive-power can be steam, compressed air, water, or horse-power. In an ordinary-sized tunnel a tread-mill horse-power can be placed on one side of the track in the tunnel, and be moved in as the tunnel is driven forward. Where a steamengine is at the surface, power can be taken from it to operate in the deepest and most extensive mine.. Where a high fall of water can be obtained, a small wheel attached to the drill gives a very convenient power. This machine has not been completed for a sufficient length of time to have worn out any of them, but the first one made has drilled nearly two thousand feet, and is apparently as good as ever. All of the parts of the different machines are alike, so that one can be substituted for another, making it very simple to repair, in case a machine should get out of order.*

The Von Schmidt drill, noticed in my report of 1871, is being constructed for running a tunnel through the Sierra Nevadas for the Lake Tahoe Water Company, and though probably of great utility, its merits have not yet been tested by actual experiment.

The sale of mineral lands and quartz ledges.-The investment of large amounts of foreign capital in the purchase and development of our gravel mines and quartz ledges is to a great extent due to the operation of the various congressional acts throwing the mineral lands in the market for occupation and purchase, whereby title may be secured, instead of holding mining property, as formerly, subject to the insecure tenure of local mining laws and usage. The following table will show the extent to which our miners have availed themselves of these acts:

* This account is taken from statements made in behalf of the inventor. I do not wish to discredit it, but merely to say that I have not verified its claims by personal examination.-R. W. R.