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to know whether a machine can be made to fulfil the promised results? We hear it strongly attested to, on the score of merit, and tied down as we are with our local duties, we cannot make the personal examinations we would desire to do, and must take the risk of relying upon the judgment of less practical friends." If the mining men would but adopt as an universal rule, that they would not purchase any machine until it had been placed upon their mine and proved by actual results to be all that its projectors had promised, they would escape the wasteful expenditure of thousands of dollars, that might better be devoted to sinking shafts, and to driving galleries upon the veins in their possession. Any company, or any individual, that entertains full confidence in their appliance, will not hesitate, upon a valid contract from the mine-holders, to purchase the machine if it will perform a stipulated amount of work, to place it upon the property, and give it a fair and impartial trial. If such a course should be adopted by any company, their own interest will prevent them from over-estimating the efficiency of their machine, as such exaggeration would render certain a failure of their contract; they would rather under-estimate its ability to work, that there might not ensue too great a risk of failure in performance.
Upon the property which has been under my management for the past year there is in use a crushing machine which was placed here under the above-named terms of contract, and which not only performs all that its proprietors claimed for it as able to do, but is capable of turning out at least twenty-five per cent. more work. It is a ponderous and simple machine, easily kept in running condition, and will readily crush from two to three tons of quartz per hour. We run it with an engine of about thirty horses' power, which also carries the amalgamating force of eight arrastres and thirty-four stirring bowls. I merely allude to the facts, and deem it but an act of simple justice to an ingenious inventor, to state, that “Bullock's Quartz Crusher" is the best adapted machine for reducing the quartzose ores to the required fineness in the shortest time of any mechanical appliance that has fallen under my observation.
It is my fondest hope and strongest desire to see the mineral value of our country correctly appreciated; and though but an humble laborer in the vast field, I am anxious to perform my portion of the great work that is to be accomplished.
The most common method of reducing the ores to a powdered state is by means of the
It is constructed by having two large and heavy stone wheels made to revolve upon a solid stone bed. Around this bed a wood work of about twelve inches in height is placed, forming a large tub, of which the stone bed constitutes the bottom. Into
this basin the ore is thrown by small portions from time to time, and is crushed by the weight of the wheels rolling over it. The stone bed is usually about six feet in diameter, and from ten to eighteen inches thick. The wheels, or "runners," as they are called, are of about the saine dimensions, and are kept in motion by suitable geering connected to an upright shaft, which is "stepped” upon the centre of the bed, and makes from six to ten revolutions per minute. The axles upon which the runners revolve are placed within a strong framework, which surrounds instead of being attached to the shaft; thus allowing sufficient vertical play to the runners while passing over the fragments of ore. The average quantity of ore crushed by one of these mills in twenty-four hours, is about forty bushels, or two tons. A stream of water enters over the rinn upon one side of the tub, and is discharged over the rim on the opposite side. This stream should be sufficient in quantity to hold the comminuted sands in suspension, and allow them to be floated off in a thin slime. If the quantity of water is insufficient the sands will pass away in so thick or muddy a condition that the specific gravity of the gold will be of no avail, and it will be carried off by me chanical suspension. If too heavy a head of water is applied the sands would be washed away, either in too coarse a state for the gold to be liberated, or too rapidly for it to be saved. A great advantage will be derived from the occasional addition of a small quantity of quicksilver to the sands in the mill. It will be found, if à fair trial is instituted, that more amalgam will be obtained from the same quantity of quicksilver applied at intervals than would be gained by adding it at one time. A positive advantage will be obtained by having the Chilian Mill so constructed that its discharge shall be through the centre. In this mill particularly, a slow and uniform rate of operation must be maintained; the work cannot be hurried without entailing a loss of gold.
In Mexico and South America the Chilian Mill is used dry. In the United States it is always used with water.
It has been suggested that greatly increased beneficial results will follow the occasional stoppage of the flow of water in the Chilian Mill operation, particularly while crushing a bed of ore. This point appears to me so feasible that I should consider it well worthy the attention of all interested.
I find that Mr. Boussingault tried at the Columbian Mines the same principle, but in the arrastre. "The mineral was put into the arrastre, with a sufficient quantity of water to give it the corisistency of a thin paste,
and was then ground for thirty-two hours,
the amalgam was obtained with great facility." Marmato, August 12, 18—.
It will be found advantageous to carry out the principle of rest, by having tanks, into which the Chilian Mill will discharge its sands or slime; it will be well to have three tanks so ar
ranged that each one will be of ample dimensions to hold from one to two days' work of the mill, and the amalgamation should not proceed until the first and second tanks are filled; then the sands should be removed from the first tank, while the third is being filled from the Chilian; and from the second while the first is refilling; by this arrangement from two to four days' rest will be allowed to all the sands.
The addition of common salt occasionally while the tanks are filling up, will be useful, from its effect to increase the oxidation of the iron usually contained in the ore. By means of a per. forated plate, similar to that used in a shower bath, a small sprinkling of water can be constantly maintained over the surface of these tanks.
Next to the Chilian Mill the most common method of crushing is effected by the use of the
Easy and simple in their construction, and in the application of power to their movements, it is not surprising that they should be found at work upon so many mining properties. They are formed usually of six pieces of timber froin four to six inches square, and about twelve feet long, armed with such a heavy iron head, and maintained in a vertical position, by a simple framework, which allows of their moving freely vertically. The motion is communicated by cams on a revolving horizontal shaft, which, lifting the stamps, alternately, to a slight elevation, allows them to fall, and, by their weight, to crush the ore placed in a trough beneath them. The size to which the ore is reduced is regulated by a grating inserted in the front of the trough, through which the slime is washed by a small stream of water allowed to follow under the stamps for that purpose. The facility with which they can be made is not their only recommendation, for on the score of efficiency they deservedly maintain a high reputation. On the same kind of ore they will do as much execution as the Chilian Mill, but they cannot, like it, be used both for crushing and amalgamating.
Upon ores in which the gold is disseminated in a state of extreme division the stamps will be found to entail a loss which would not arise under a crushing process; still, I think, if the system of “rest” should be allowed immediately after the stamp work, much of the loss of minute gold would be prevented. On ores containing particles of coarse gold, if the grate is set coarse, the stamps will prove to be a valuable method of reducing the rock to sand. Stamps are used with water or without it, as suits the views or fancy of those using them. There is a considerable difference of opinion among those who use the stamps, as to which branch, the wet or dry, belongs the superiority. I am inclined to favor the wet process for all kinds of ore. I believe
less gold is lost by the wet method than by the dry; and much testimony can be induced in favor of its greater economy on the score of cost. The following extract from Mr. Harkort's Report to the Bolanos Association in 1830, is decisive on this point ;“The costs of a dry stamp work, by the Mexican process, on 1,000 quintals is $124, while the cost of wet (German) stamp work on 1,500 or 2,000 quintals weekly, at the hiç hest would be but $24, saving $100 on each torta, and the loss by amalgamation less, as the flour become much finer than by dry stamping."
Perhaps it would not be out of place at this point to present a brief view of the Mexican treatment of ores. The ores when taken from the mine are broken in small fragments, and separated as well as can readily be done, from the gangue-stone. They are then passed through the stamps; usually the dry stamps. Then they are worked in the arrastre; afterward gathered into flattened circular heaps, called “tortas," on a close pavement, and thoroughly intermixed with common salt, the tendency of which is to assist in the decomposition of the iron pyrites, by forming a muriate of iron. Quicksilver is freely sprinkled upon and incorporated into the mass; a second and a third quantity of quicksilver is added until there is enough to take up the gold contained in the slime of the “torta.” The slime is then washed in a vat, and kept constantly agitated, by which means the lighter impurity or earthy matter, is floated away by the discharge trough at the surface, and the amalgam remains at the bottom of the vat, from which it is easily gathered after drawing off the water. From the above brief outline it will be perceived that the Mexican process involves a continued succession of
rests for the ores; allowing time for the gold to subside, and time for the arnalgamation to proceed.
Constant care and attention are necessary upon the part of the stamp-tender to see that the supply of ore is regular both as to time and quantity. If, through a desire to gain for himself some extra moments of leisure, the stamp-feeder should throw under the stamps an over supply of ore, the water will be so thickened with the mud and sand that the gold will not fall through it, but be carried off by being held in suspension in the muddy mixture. If, through neglect of duty, he omits to fur. nish the necessary quantity of ore to the stamps, the too rapid flow of the clear water will carry away the fine particles of gold by its greater force.
As in the case of the Chilian Mill, I would repeat here, even at the risk of being charged with tautology, that the work cannot be hurried ; that it must be slow and regular, and that any deviation from this course will entail a corresponding loss of gold.
S. P. I. To be continued.)
Art. III.-A GEOLOGICAL RECONNOISSANCE OF THE STATE OF
We are pleased to notice another State Report, another of the finger-marks of our age. This Reconnoissance is, as the title-page announces, " The First Biennial Report presented to the Thirty-first General Assembly of Tennessee, December, 1855, by James M. Saf. ford, State Geologist
, Professor of Natural Science in Cumberland University, Lebanon, Tenn., &c.'
Tennessee was early in the field with her State Exploration, having been preceded only by North Carolina, South Carolina, and Massachusetts, of which latter State Tennessee was only some two or three years posterior. In 1839 Professor Troost published a Geological map of the State, and up to 1845 had made some seven or eight annual reports; some of the later ones, however, being merely pamphlets, as might have been expected from a Legislature which, from the meanest parsimony, tolerated rather than encouraged the exploration of her own resources.
In elucidating the geology of the State, Prof. Safford has adopted for inceptive operations a Reconnoissance, or General Survey of the whole State. This mode of commencing the survey was the result mainly of a suggestive, or, perhaps, constrain. ing public sentiment, and measurably of a conviction of its utility and adaptability to the popular apprehension.
This plan may be a good one, and certainly is so, prima facie, but is it a reliable one? Is it not too subject to the uncertainties of superficial explorations, of comparatively new ground; and until detailed examinations have detected all the analyses of older and better known fields of geological research, is it not too liable to changes and differences of allocation? We would not except to it here, however, but suggest the question of its expediency as one yet to be decided by competent authority. The utilities of the plan in the present survey have certainly been many, and of great practical value.
It has presented, in a comprehensive style, by a finely furnished and scientific mind, an outline of the geognosy and mineral values of the State. It has grouped the cominon characteristics of distinct regions, designated points of special interest for detailed examinations, and cleared the way for future economic explorations. As Prof. Safford well says, “ Geological formations are the great storehouses of mineral treasures, and the determination of the position, extent and mineral contents of these great repositories was a leading object in the reconnoissance. Dr. Troost, who had acted as State Geologist before Prof. Safford, did much to open the way for subsequent explorations, and Prof. Safford says, " that Dr. Troost's researches, although he never had the means to give them that scope and utility desirable, have never