The alkaline salt potash is so important in agriculture and the arts, that we think a full explanation of the method of obtaining it in large quantities from a new source will be interesting to the readers of the Journal. Potash, as is well known, was formerly the cheapest of the alkalies, but it is now the dearest; and in every possible case its place has been filled by one of the other alkalies, usually soda. The principal, and, for a long time, the only source of potash, has been the ashes of plants ; but within a short time, potash salts have been discovered in vast amounts at the salt mines of Stassfurt, Prussia. Their value was not at first recognized,but did not long escape the notice of the very eminent chemist, Henrich Rose, who pointed out their importance. At the present time they are extensively worked. They are found overlying the salt beds in layers of various thicknesses, and are associated with salts of lime and magnesia. The principal forms in which they occur are known as mineral species under the names of polyhalite, sylvite, carnallite and kainite; accompanying them are found rock-salt, anhydrite, kieserite, tachydrite, and boracite. Polyhalite is a hydrated sulphate of potash, lime, and magnesia ; sylvite is chloride of potassium; carnallite, a double chloride of magnesium and potassium ; and kainite, a compound of hydrated chloride of potassium and sulphate of magnesia. Of the associated minerals, it need hardly be said that anhydrite is the anhydrous form of sulphate of lime ; kieserite is a hydrated sulphate of magnesia; tachydrite, a double chloride of calcium and magnesium; and boracite, a borate of magnesia Carnallite is the material worked for the extraction of potash. It is found mixed with rock-salt, kieserite, and small quantities of the other species mentioned above. As the mineral comes from the mine, it contains about one-sixth its weight of the potassium salt (the chloride) the ' rest being rock-salt and the chloride of magnesium, which is combined with the potassium salt as carnallite. In the process used to get the chloride of potassium in a reasonable degree of purity, advantage is taken of the different degrees of solubility of the various substances with which it is associated. The chlorides of potassium and magnesium are much more soluble than the chloride of sodium ; so by treating the salt mass with an insufficient quantity of hot water, the two first-named salts are dissolved, while the most of the common salt is left behind undissolved. Chloride of magnesium is very soluble in cold water, and common salt is equally soluble in hot and cold water, so that both these remain in solution, while the potassium salt crystallizes out in a state of tolerable purity, about 80 or 90 per cent of chloride. This product is good enough for commercial purposes and is used for making other salts. By further concentration of the mother liquor, the original salt, carnallite, deposits, and can be again worked over, while chloride of magnesium only is left in the solution. From the chloride of potassium the sulphate can be prepared by treatment with sulphuric acid ; and from the sulphate the carbonated and caustic alkali, by Leblanc's process. This method, however, requires the use of a material (the acid), which is obtainable at the mines only at a considerable expense. It was therefore desirable to employ, if possible, the natural sulphate of magnesia, which is very plentiful at Stassfurt. After a great deal of experimenting, this was finally accomplished in a very ingenious manner by the formation of a double sulphate of potash and magnesia. This is done by simply adding sulphate of magnesia to the solution of chloride of potassium, a double decomposition taking place, with the production of sulphate of potash and chloride of magnesium. But the sulphate of magnesia, as mined, is mixed with common salt, from which it must first be freed. The mixture of rock-salt and sulphate of magnesia is placed in water. The magnesia sulphate is but slightly soluble in the brine which is soon formed and collects at the bottom of the vessel, from which it is removed and used to form the double salt above mentioned. By careful treatment of the double salt, a part of the sulphate of magnesia may be got rid of, and from the residue carbonate of potash produced by Leblanc's process. Another mode of treating this double salt is by a solution of chloride of potassium, and then, by a series of crystallizations, are obtained pure sulphate of potash, the double sulphate again, and a double chloride of potassium and magnesium (carnallite.) The sulphate of potash is of course fit for the market, but the other salts are again worked overc,in the ways previously described. As already_stated, the deposits at Stassfurt are of enormous extent, and from them potash and its salts are now produced in such great quantities that their cost has been very materially lessened, so that even in agriculture they can be advantageously used. The processes employed for their extraction seem simple, and indeed are not very complex, yet are of a very interesting character, must be carried on with care and judgment, and require skill in manipulation. Separations of the kind we have been describing, are only possible on a large scale. One of the most important points connected with them is the manner in which the various mother liquors are brought into use. For instance, if the raw mass of rock-salt, 'chloride of potassium, and magnesia salts, instead of being treated with pure water, is acted upon by a mother liquor, already saturated With the two former, it is evident that almost all of the magnesia compounds will be dissolved, leaving the alkaline chlorides behind. Again, in the process given above, by which pure sulphate of potash is obtained, it will be noticed that at the same time other salts are formed, only to be worked over again. The final mother liquors contain very little beside!!' magnesia salts, and are utilized to some extent as a source of magnesia.—Journal of Chemistry. S(i'pJlratlng Animal from Vegetable Fiber. In mixed fabrics or fabrics composed partly of animal and partly of vegetable fibers, the separation of animal fibers, such as, for example, wool, hair, or silk, from the vegetable fibers, such as cotton, flax, or j ute, is a process necessary for certain purposes. The plan hitherto adopted for the purpose of separating these fibers has been to treat the material to be operated upon with acids. This is, however, objectionable, as the animal fiber is by their action rotted, and thereby loses its milling and felting properties. In a recent patent, Mr. James Stuart, of 40 Ropemakers' Fields, Limehouse, dispenses with these acids, and substitutes neutral substances. In this way rags, carpet cuttings, old carpet, and other waste material of mixed fibers may be utilized to a greater extent than has hitherto been found practicable, and, as the separated animal fiber retains in most cases its color, it can oftentimes be worked up again ,into articles for use without the necessity of its being re-dyed. His invention consists in subjecting rags, carpet cuttings, old carpet, or other material of animal and vegetable fiber intermixed to the action of chlorides of the metals or sulphates of the oxides of the metals, preferring, however, to use as the active agent the chloride of aluminum. In thus treating the material, certain chemical reactions take place whereby the vegetable fiber is decomposed and the animal fiber is recovered uninjured either in substance or,in color. It is then in a fit state to be re-manufactured without re-carding, spinning, dyeing, or other operations that have hitherto been necessitated. In practice, Mr. Stuart first makes a solution of ingredients in the following proportions : In 100 gallons of hot water dissolve 100 lbs. of the suphate of alumina of commerce; then add 50 lbs. of chloride of sodium : when this last-named ingredient is added, a reaction takes place ; sulphate of soda is formed, and also chloride of aluminum. With the solution thus made the material to be treated is saturated. It is then drained so as to allow the excess of the solution to pass therefrom ; or the material may be slightly wrung or pressed for the same purpose. The material is next dried and after, wards exposed to a steady temperature of 200° ' Fah. During the time of this exposure, the chloride of aluminum decomposes, and the resulting volatile products, as they pass off, act upon the vegetable fiber, rotting them, but leaving the animal fiber uninjured. The material treated is then scribbled, and the vegetable matter separates in the form of dust. This treatment refers more particularly to rags of light mixed fabrics. When treating heavier or denser material, such as carpet cuttings or old carpet, the solution of chloride of aluminum is of greater strength. In 100 gallons of water dissolve 150 lbs. in weight of sulphate of alumina and 75 lbs. of chloride of sodium, and then proceed in the manner before described. In some cases, it is found more convenient to treat the material by boiling than by heating in drying rooms. Mr, Stuart then proceeds in the following manner: He makes a solution of sulphate of alumina by dissolving 100 lbs. of that substance in 100 gallons of water, and with this solution he saturates the material. It is then drained, and afterwards placed in a boiling saturated solution of common, salt. In this solution the material is kept boiling until the vegetable fiber is' decomposed or rotted ; the material is then well washed and dried, and scribbled or carded.—Mechanics' Maga- eine. The Danford Steam Generator. The Joliet, Ill., Republican, in speaking of the above generator, says : Had it been in use at the Indianapolis State Fair, the columns of the press all over the country would have been filled with pleasanter matter for perusal than the heart-rending tales of that sad disaster. Our investigations of it were of such a satisfactory character that we have already purchased a generator and engine, and are this week placing it in our establishment to run our presses, and we do not hesitate to recommend it to every one who uses steam power as being absolutely safe. 'Ihe novelty of the Danford Steam Generator consists in its being a hollow wrought iron cylinder of 5-8th inch thickness, the side and heads welded together. This is placed in a jacket or furnace lined with fire brick ; the back wall of the furnace is so constructed as to throw the heat and smoke around the cylinder or generator, which is made by a simple process to revolve, creating a draft, helping to consume the gases and smoke, and what is more important, equalizes the heat on the generator, making the iron to last much longer. We have been shown iron subject to this test for twelve months, after which it was softer and better than the day it was put in. The fire to heat the generator and make the steam is placed in the furnace, immediately under it, playing on the bottom of the circle as it revolves. . By putting a three-fourth inch water pipe through the generator from end to end, plugging up the end from the engine and perforating it with 330 or 40 smaU holes the size of a pin head, you have the machine ready for use. To make steam by this invention is so simple, and still so effective, that it wins you as a friend at once. To make a fire in the furnace and heat the empty generator is but the work of a very few moments, after which you work a temporary handle attached to the pump, and by a few strokes you raise the pressure to 100 pounds. after which you are ready to operate with your engine, which makes the necessary steam to run it and keep up the reserve at every revcV.-tion by throwing a sufficient amount of water through the boles in the water pipe in the condition of spray, which is instantly flashed into steam, thereby keeping a regular pressure on the generator. The generator or cylinder never contains any water to be suddenly expanded into a large body of steam, and is, therefore, to our judgment and others' experience, absolutely Ma- explosive, and as the steam made is superheated, almost any desired pressure can be obtained and used with safety. T0 our knowledge steam by this machine has been made and used up to 300 pounds pressure to the square inch without fear or danger. We are glad to learn from Mr. George P. Jones, Secretary of the Company at Chicago, Ill., that this improvement, patented in this country and in Europe through the Scientific American Patent Agency, “ is now a practical success." SomethlJlg New in Working- Plaster of Paris. We find the following in the Druggists Circular: ” It is a well-known fact that ,powdered gypsum, when freed by calcination of its water of crystallization, Yegains to a great extent its original hardness when incorporated with water enough to form a stiff paste. In order to attain this end, there is at least thirty-three per cent of water requir©d wherefrom twenty-two per cent is withheld as water of crystallization. The rest evaporates, and thus brings about the porosity of the hardened gypsum. In working up a small quantity of gypsum, one has only a few minutes' time for using the paste for molding or puttying, as it soon becomes hard. With larger quantities, in which case the making of the paste requires a longer time, the mass hardens, sometimes, during the operation of dressing. According to Mr. Puscher, of Nuremburg, this inconvenience may be gof rid of by mixing with the dry powdered gypsum from tw0 to four per cent of finely pulverized 1 althea-root, (marsh mallow) and kneading the intimate mixture to paste with forty per cent of water. In coJlsequence of the' great amount of pectin which is contained in the althe».:rOot, and which iIl fact amounts to about fifty per cent, a mass similar to fat clay is obtained. This mixture begins to harden only after a lapse of one hour's time. Moreover, when dry it may be filed, cut, twined, bored, and thus become of use in the making of domino-stones, dies, brooches, snuff-boxes, and a variety of otlier things of a similar character, Eight per cent of althea-root, when mixed with pulverizoed gypsum, retardg the hardening for a still lopger time, but increases the te^. acity of the mass. The latter may be rolled out on wind0w- glass into thin sheets, which never crack in drying, may be easily detached from the glass, and take on a polish readill” uP°» robbing them, This material, if incorporated w^l” mineral or other paints, and properly kneaded, gives very fine imitations of marble. They bear coloring also -when dry, and can then be made water-proof by polishing and varnishing. The artisan, in the practice of his trade, wiJl probably find it to his advantage to make use of this prepared o-ypsum in place of that usually employed by him ; the manufacture of frames need have no fear that hi? waieS will crack if he uses a mixture of the above-indicated composition ; more- wer the chemist and chemical manufacturer will find that the same does excellent servise in luting vessels of every kind. The exact proportion of water to be m«de use of cannot be given exactly, as it vanes within a few per cent according to the fineness and purity of the gypsum employed. The above-mentioned althea-root niled not be of the very best qu^ty the ordinary kind serving the purpose perhaps quite as well," Improved Wagon Tongue. The object of this invention is to furnish a spring support for wagon tongues. It is without doubt much superior to the old method; avoiding all humping, and adding to the comfort of horses, driver, and passengers. A, in the accompanying engraving of this invention, is a piece bolted or screwed to the under side of the tongue, to which is pivoted the rod, B, extending back beneath the tongue to a cylindrical rubber spring, D. A collar, C, with nut running upon the rod, B, serves to adjust the support to hold the tongue at the proper hi'ght. The rod, B, passes through the center of the rubber spring and through an eye in the center of the oscillating cross head, E. This oscillating cross-head permits all the necessary oscillation of the tongue and the support without allowing the tongue to hammer upon the neck-yoke, or hold-bac^ supports, thus relieving the necks of the horses. The oscillating cross-head is pivoted to curved supporting bars, F. \ These are all the parts of the device which seems simple and serviceable. Patented through the Scientific American Patent Agency, Sept. 21, 1869, by George Alexander, of Romney, Ind., who may be ad” dressed for exclusive rights to manufacture in the United States. absorbs gas from the sewer, and gives it off into the house, and, if there be any-pressure, the trap is forced. Neither is it of any use to say that sewers ought to be self-cleansing, that they ought to form no deposit and give off no gas. What ought to be, and what actually is i^ this wicked world are two very different things. The real plan is to ventilate every sewer abundantly ; to have a rapid and constant circulation of air through it ; so that the sewer gas may be diluted and decomposed as soon as formed. In order to effect this, in the first place every house drain ought to be ventilated by carrying up the soil pipe to the highest available point, so that it be far enough removed Suspension Bridges in China. The construction of suspension bridges has been thought a signal achievement by the Western nations, but in China they are of great antiquity, and many still exist. They are made of iron chains, and their mode of construction resembles, in the main, that used in the Western countries. They are, however, generally confined to the mountainous regions, and span ri^^s whose navigation is interrupted. There is one over a river in the Yunnan province that is said to have been first built by one famous Chu-koh-hand more than two thousand years ago ; and there is a second and much larger one in the Kwelchow province, spanning the river Pei. This latter Was built during the Ming dynasty. It consists of I many chains stretched across the river and fastened firmly in /' the stone on either bank ; from natural elevations above, other chains depend, and are made fast to the span, and there are also chains fastened to it from below, the object being to make the bridge as firm as possible. A plank floor is laid on this bed of chains; it is repaired at regular intervals of from three to five years at the imperial expense. The span of this bridge is said to be several hundred feet. ” Ventilate your Sewers! Do not Trap!" These words form the close of a very valuable address on the influence of sewer' vapor on health, delivered by Dr. Carpenter, of Croydon, before the Social Science Association, and we think the substance of it deserves the widest circulation. It is within the memory of this generation that typhoid fever has been distinguished from other fevers, and has been traced to sewage. The earliest efforts of sanitarians were directed to the abolition of those collections of impurity in cesspools which formerly poisoned the earth, air, and water for our forefathers ; and with the introduction of water- closets and of tubular drainage, it was hoped that typhoid fever, at least, might be exterminated. Nevertheless, it did recur again and again, a\ at Croydon ; because, says Dr. Carpenter : ” In the early sanitary works which were carried out under the supervision and with the approval of the General Board of Health, and uader the authority of the Public Health Act of 1848, the consequences of sewer gas not being foreseen were not guarded against ; no provisions were made to prevent its ascent into the house, or for exit into the open air before it could reach the inside of the dwelling'. The rapid spread of luxurious habits among the people, the introduction of low fireplaces and register stoves, and the method adopted to exclude drafts- by having exceedingly close-fitting windows and doors, prevented the easy exit, and its baneful influence became manifest, often without the real \Jause being at that time at all suspected. It often happens that the easiest way for air to enter the house is by the sewer. “ Then, with this state of things, “ fever would recur ; fever always the same in type, 'the enteric ®r typhoid' form, with rose-colored spots, often with abdominal complications, and always in those houses nearest to the top of the sewer (per - haps I should say generally), and farthest from the outfall." Nor is fever the only consequence of the entry of sewer gas into dwelling houses. “ Many other disorders of the system,” says Dr. Carpenter, “ have been directly traced to its influence —thus diarrhea; dyspepsia in all its forms ; palpitation of the heart ; various forms of asthma (indeed, it may help to explain some of the vagaries of this curious disease) ; convulsions, especially in teething infants ; hea laches, both persistent and intermittent. The evils which sometimes attend or follow upon the puerperal state, as milk fever, abscesses in the breast, and phlegmasia dolens or white leg, are frequently caused by it. I believe that these latter cases have been so associated, from observing their frequent occurrence in new houses before the plan now adopted in our district was carried out." How, then, ;s this enemy so subtile and deadly to be dealt with ? Most sanitarians have hat one reply—put efficient traps and shut out the gas. Trapping alone, Dr. Carpenter concludes, is delusive ; for ,not only may the trap become dry, but the water that seals it ALEXANDER'S IMPROVED WAGON TONGUE, from windows and chimneys. Other ventilating shafts, straight and perpendicular, ought to be put to every pipe requiring a trap, so as to protect the trap from the effects of pressure. Then, instead of closing the apertures into the street sewers, they ought to be as many and as open as passible. Stagnation in sewers, whether of solid, or liquid, or gas, must be. avoided, and, considering that the sewers have a higher temperature than the air above, there is sure to be a rapid circulation through them if openings enough be provided ; and public safety may be consulted by placing charcoal ventilators in the line of the up currents.—New York Medical Journal.