stronger force; and if we increase that force, so that it shall bear to the other the ratio of A E to A D, A F, the path of the body will be still more nearly coincident with A E. Whence it follows that a moving body resists diversion from the direction in which it is moving, and this resistance is in the compound ratio of its quantity of matter and velocity. If we apply this principle to a wheel or other body revolving on an axis, and, leaving out of view the thickness of the revolving body, consider that the centrifugal force tends to impel every particle in the direction of a tangent to the periphery of the circle in which it revolves, and that all these tangents lie in the same plane, (perpendicular to the axis of revolution,) we can readily perceive that the revolving body will resist any change of its plane of revolution, or, (which is the same thing,) of the direction of its axis, with a power proportioned to the momentum generated by its revolution. If we take the thickness of the wheel into account, we find the particles revolving in a series of parallel planes, with a like tendency to resist change. It is this principle which gives to rifled fire-arms their chief advantage in point of accuracy. If we regard the projectile discharged from a piece of this description as moving in a right line, (which is virtually true of short distances,) its plane of revolution is at right angles to its line of progression; in other words, the axis of revolution coincides with the line of projection. It is evident that the tendency of revolving bodies to preserve the identity or parallelism of their planes of revolution, and, consequently, to maintain the direction of their axes, strongly operates to continue the ball in the line of the original impulsion. If we apply this law to the gyroscope, it will readily be observed in what manner it co-operates in preventing the wheel from falling. For, one end of the spindle being sustained by the upright pivot, the wheel can only fall by describing the arc of a circle, the centre of which is the point of the pivot and the radius, the spindle. But to fall in this manner, requires a constant change of the wheel's plane of revolution, the tendency to resist which has already been explained. For the Journal of the Franklin Institute. A New Process for Extracting Gold from Auriferous Ores, and particularly applicable with great advantage to Pyrites and other Ores containing Gold in small quantities. By H. JACKSON and W. A. OTT. Amongst the different improvements lately adopted for the extraction of gold from auriferous ores, the process of Professor Plattner, of Freiberg, (Saxony,) occupies the first range, as well for its ingenuity as for the advantages to be derived from the same. In this country, on the contrary, the quicksilver or amalgamation process is almost universally practised, and each improvement which possibly could be made has been adopted, so that it may be said the process of amalgamation has arrived at a point where still better results cannot be expected. Though well known and extensively practised for many years, nevertheless it is not free from considerable defects, which, in relation to economy, never will be obviated. This is a fact generally acknowledged, and the process of amalgamation would have been abandoned if there should exist a more practical and improved mode of extracting gold. The said process of amalgamation cannot be applied advantageously to the treatment of poor ores on account of the great division or distribution of the gold, thus causing an imperfect contact with the quicksilver, and consequently an imperfect amalgamation. Numerous trials and experiments have proved the impossibility of avoiding these defects, even if the operations of the amalgamation are conducted with the most scrupulous care. For these reasons Professor Plattner, one of our most ingenious metallurgists, suggested the extraction of gold by means of chlorine, which has been introduced at Reichenstein, (Prussian Silesia,) where immense quantities of certain auriferous residues from the preparation of arsenic had been accumulated since several centuries. These residues being extremely poor of gold, and not fit for being treated by any other known means, nevertheless afforded a considerable profit by the treatment with chlorine. The same satisfactory results have been obtained at Schemnitz and Schmollnitz in Hungaria, and other localities, where large hills of residue, formerly considered worthless and thrown aside, are worked over again and every trace of gold extracted. Plattner, perfectly posted up in theory and practice of all metallurgical operations, soon came to the conclusion that his process might undergo an alteration or improvement in relation to the treatment of natural ores, and especially such ores as contain the gold in a mineralized condition, but, by his premature death, he was prevented from finding out such improvements. Since Plattner's death nobody on the other side of the Atlantic has taken particular pains to apply his process to the treatment of natural ores, for the reason that gold-bearing ores are comparatively rare in Europe. In order to explain the defects of this process, we deem it necessary to go into some details, and to report afterwards on the method of extracting gold, for which letters patent of the United States have been granted to us in the month of April, 1865. Previous to the treatment of chlorine, the ores must be pulverized as finely as those which shall be submitted to the process of amalgamation. Ores containing sulphur must be roasted until all other metals contained therein have been transferred to the highest point of oxidation, being in this condition but very little attacked from chlorine, while gold almost alone will be dissolved. The ore thus first prepared is carried into earthen jars or wooden barrels lined inside with lead, and chlorine gas is passed through the ore so as to impregnate it thoroughly. After this operation, lukewarm water is to be poured over VOL. L.-THIRD SERIES.-No. 1.—JULY, 1865. the ore; the resulting filtered lye of gold is precipitated by sulphohydrogen, and the precipitate thus obtained from the sulpho-combination of gold and other metals is dissolved in aqua regis, and by an addition of sulphate of iron the metallic gold will be obtained in a finely divided condition, free from silver or copper and fit for direct melting. This treatment answers perfectly well for quartz containing gold in very small particles, and for ores containing very few sulpho-metals, and requiring no completely and costly desulphurization, and it answers also for residues, though the apparatus prescribed by the inventor does not allow operations but on a small scale. For treating ores rich in sulpho-metals, like our ores from Colorado, the application of the said process meets with two serious inconveniences, viz: 1. An excess of chlorine is necessary, and 2. The remaining ore is very seldom completely exhausted and contains still some gold. If we examine specially these two faults, we find that the cheapest mode of chlorinizing would be, if just as much of the chlorine gas could be used as might be necessary for the dissolution of the quantities of gold contained in a certain ore. But that, perhaps, never will be the case, and we always shall need a large portion of chlorine; whereas the finely divided ore, and particularly the oxides therein contained, will absorb the gas without binding it chemically. According to Plattner's plan of treating the ore, a considerable quantity of gas must be lost, and consequently the expenses will be increased the more as the ability of the ore for absorbing the gas may be very strong, and as the prices of the acids and other materials necessary for the preparation of the gas may range high. If this inconvenience cannot be set aside completely, it is, however, possible to do so partially in a manner we cannot describe here more particularly. It may be enough to mention that, by applying a peculiar desulphurizing process, we save near one-half of the amount of gas from that required at the works of Reichenstein. This is the first advantage afforded by our process. In Plattner's process another inconvenience is to be found in the following: In consequence of an imperfect roasting and of the existence of basic salts and sulpho-metals, combinations of chlorine and sulphur may be created, which, while producing a secondary decomposition, will exert an influence on the chloride of gold already formed, and will separate a quantity of the metallic gold proportional to the quantity of the sulphur, thus being lost for the process. A complete roasting, going as far as to remove every trace of sulphur, no doubt would be the best means of obviating this inconvenience, but whoever knows the difficulties occurring in the practice, particularly when operating on copper pyrites, will give up the execution of such a plan. In our process we obviate the precipitation of the gold in a different manner, that is, by substituting hypochlorous acid (a gaseous body consisting of 1 eq. chlorine and 1 eq. oxygen) for the chlorine gas, and by submitting the ore to the effects of this gas. The hypochlorous acid gas, when brought in contact with the combinations of sulphur remaining in the ore experiences a decomposition, the oxygen uniting with the sulphur and transferring it into the highest degree of oxidation while the chlorine combines with the gold. By the application of the said gas to the process of extracting gold, we are enabled to secure two important advantages, namely: 1. We obviate entirely the formation of injurious agents by means of the oxidizing effect of the oxygen, and 2. The chlorine is acting while in statu nascent. In this state the chlorine has reached the highest degree of chemical affinity, thus making our process (besides its ability of promoting the close of the operation) applicable as well to ores containing gold in finely distributed particles, as to such ores which may contain gold in coarser particles. Having explained the two chief points which distinguish our process from Plattner's mode, we deem it necessary to say a few words in regard to the question whether it is applicable in a large scale. Our process requires, like all others, a complete pulverization, and next a good roasting, if the ore should contain sulphur. In case the ores should contain copper, it would be advisable to submit them to a roasting, and to extract the formed copper salt by water, and to precipitate the copper by proper means. In both cases the ore is ready for being treated by the hypochlorous acid. The question now arises whether this gas can be produced at a sufficiently cheap rate. In view of the enormous quantities of it produced for the preparation of bleaching salts and especially of chloride of lime, we may confidently give an affirmative answer. We do not need for our purposes any other apparatus or localities than those required for the manufacture of the before-mentioned articles, except a leaden retort, which should be placed between the generator of the chlorine and the buildings for the storage of the ore. retort is filled with a solution of sulphate of soda or glaubersalts, and we thus obtain the hypochlorous acid in a free condition. This The generator of the chlorine in proportion to the impregnating chamber requires smaller dimensions than those necessary for the manufacture of chloride of lime. The impregnating chamber is constructed from silicious sandstone or from bricks in a longitudinal form, and represents a room rather more high than wide. It must be coated inside with asphaltum, and boards 8 to 10 feet long and 2 feet wide should be fastened horizontally along the large sides, one above the other, allowing spaces of about 4 inches between them. These boards are designated for receiving the ore. In the middle of the building a small gangway is to be left; two windows allow to watch the operation, and one door affords admittance to the chamber. A green color will be observed at the windows when the impregnation is completed, and the door thus far tightly closed, then may be opened for the exit of the gas and for the removal of the ore. The next operation, i.e., the extraction of the ore, is performed either by centrifugal power or by a hydraulic press and water. In this manner we obtain a very concentrated lye from which we precipitate the gold either directly by sulphate of iron, or by a treatment with sulphohydrogen and subsequently by sulphate of iron. Both operations are very simple and do not require any particular or costly apparatus. Compared with the process of amalgamation, and in consideration. of the expenses for putting up such an establishment being equal, our process, besides the before-mentioned advantages, affords still others, viz: 1. The value of the materials entirely disappearing out of the operations is considerably less, whereas we are working with materials far cheaper than quicksilver. 2. We save great expense of fuel, indispensable for the distillation of the quicksilver. 3. We need no refining, pure gold being precipitated from the solution of the chloride of gold. 4. Our process is not injurious at all to the health of the operators. Atmospheric Pressure as a Source of Mechanical Power. Fully to appreciate the value of atmospheric pressure as a source of mechanical power, it should be considered not only in contrast but in connexion with the steam engine, and to that the present section is given. There are some points about steam not generally known, or if known seldom thought of. 1. Quantity for quantity, low steam costs the same in fuel as high steam; or, as laid down in the books, "The same quantity of heat is sufficient to convert the same weight of water into steam whatever be the pressure under which the water is boiled, or whatever the pressure and density of the steam produced." 2. There is the same force in the lowest as in the highest steam; the condensation of the former under a piston exciting an amount of atmospheric pressure equal to the expansive force of the latter against it. In other words, "the same quantity of water converted into steam produces the same mechanical effect whatever be the pressure or the density of the steam." 3. There is no augmenting the natural power of steam. As well might we think of increasing the weight of the atmosphere. To obtain more power from it we call into action more of it, and that is the only means by which additional power is to be had from it. Its force rises and falls with its quantity. A quart compressed into the space of a pint exerts an intenser force than when in the quart, but it is on a smaller surface. The pint can do no more work than the quart. One law governs all forces. A pound weight on a lever |