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which they are turned round ana the screws forced up to their firm bearing. The first 60 or 100 feet is bored to the diameter of about 2£ inches, and is cleaned out by a gouge of 2£ inches in diameter; the whole is then widened by a chisel, 4 inches in diameter, furnished with a guide for keeping it perpendicular.

The vertical or jumping motion of the tool is often obtained by a windlass instead of the simple plan just noticed. The rods are suspended to the windlass by a rope coiled two or three times round it, and so adjusted, that if the man holds one end of the coil tight, there will be sufficient friction to raise the rods on putting the windlass in motion. On slackening the end of the rope held by the man, the coil becomes loose, and the rods descend with a force equivalent to their weight and the distance through which they have fallen. In this way a regular percussive action is gained by keeping the windlass continually in motion in one direction, while the workman alternately allows the rods to be drawn up a certain distance, and then by relaxing his hold allowing them to fall.

Instead of the arrangement of poles, Fig. 193, it is often desirable to erect a stage over the proposed boring. This stage consists of a stout plank floor, resting on strong puttocks, and well braced together by planks nailed transversely across. In the centre of this floor is a square hole, a little larger than the boring-rods, but not large enough to allow the hook, Fig. 195, to pass through. Wooden trunks or temporary iron pipes arc fixed under the boring stage, as guides for the boring tools and permanent pipes, &C. The permanent pipes to be inserted into the bore are joined together and slung ready to be fixed when required. If the bui ? be through mottled clay, the sooner the pipes follow, tho better, as the sand underneath is apt to blow up into the bore-hole, or the clay itself, if not stiff, may choke up the hole. These pipes arc either of cast or wrought iron; the latter being generally used for small distances, and the former, being thicker, are used for very deep work, where much driving is required. The lower pipes of the series are usually perforated with small holes, when the spring is in sand; but when water rises from chalk or rock, no perforation is required, and the pipes themselves arc only required to keep the hole open. In many cases in and about London, advantage is taken both of the main sand-spring and of the chalk-springs also: the perforated pipes arc firmly driven into the former, and smaller pipes and a smaller bore are continued to the chalk. A length of wrought and east-iron pipe is shown in Fig. 198. The junctions of the pipes have nearly, and, in some cases, quite, an even face on the outside. The cast-iron pipes have generally turned joints and wrought-iron collars,

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Fig. 201

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usually flush inside as well as out. The collars are sometimes fixed on the pipes with screws; but when the joints arc not turned, they are run together with metal, a plan which shuts out bad water on the outside. The wrought-iron pipes are seldom riveted, but have thin collars soldered on, not quite flush outside, and the melting of the solder previously run in the parts is effected by suspending an iron heater, Fig. l,} '' 199, down the pipe. The pipes are slung down the well by means of a wooden plug, Fig. 200, with a pin or key passing through it; and this being inserted into the end of the pipe, which is cut reversely, as in Fig. 201, will clearly hold it, and by merely turning round the plug after slacking it, the pipes will be detached. By this plug also the pipes can be driven. This small groove can be used at any depth, and where it is completely out of sight of the workman. i

Some of the tools used in boring are shown in the following figures :—

Figs. 202, 203, show an elevation and section of* an auger. The tapped socket is to allow the rods to be screwed into it. A usual form of handle for turning round the rods is shown in Fig. 204. The leading nose is for cutting, and there is a valve within the cylinder for preventing the material cut from falling out when the auger is raised. Fig. 205 shows a small auger, with a longitndinal slit, and no valve: it is used for boring through clay and loam. In very stiff clay the slit may bo Fig. 204.

wide; in soft clay, narrow; but in very moist ground this tool cannot be used. The lower figure is a plan, or horizontal section, of this tool. Fig. 206 represents an S chisel, for cutting through rocks, flints, etc. This tool is worked with a vertical motion, and in a circular direction. In boring through sand, or hard ground previously loosened by other tools, a large shell, shown in section, Fig. 207, is used: it contains two valves, opening upwards, one of which is shown in the figure. Fig. 208 is a spring rymer, in which the cutting edges arc placed reversely, and the size is regulated by means of the screw and swivel. This tool is used for enlarging a hole. When the pipes arc inserted some distance, it is important to widen the bore under them, to allow them to be driven further: this tool is therefore forced down the pipe in a partly collapsed state, springing to its set

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When very soft sand is met with, a tool fashioned like a common lifting pump is used; a vertical upand-down motion filling the body of the tool with the soft matter. A useful boxing tool for hard substances is a hollow cone, Fig. 215, with a spiral winding round it: as the boring goes on, the material accumulates in this cone, and may thus be raised to the working-stage.

In some cases, to ensure the vertical direction of the boring tools, guides are required: these are formed by bolting either to the tools or rods four wrought-iron bars, bent at the ends, so as exactly to fit the hole between the extremities.

One of the greatest difficulties in boring arises Fig 20g Fig. 2io. ^rom *nc occasional breaking of

Hig the rods. In order to extricate pi them tools have been contrived. L' Rg. 200 is a spring lateh-tool, in which the forked hinge shuts by the action of a spring; so that when the tool is forced over the knob of the broken rod, as in the figure, the spring shuts the forked hinge under the knob, by which means the broken rod can be raised. When the knob cannot be easily got hold of, a screw, Fig. 210, is used. This tool is also applied when theweight to be raised will not overcome the friction of the screw.

Various other tools used in boring are described in works devoted to this branch of engineering, among which we may especially refer to M. Garnicr's "Puits Artesiens," 4to. Paris, 1826. An excellent little "Treatise on Well-digging, Boring, and Pump-work," by Mr. Swindell, is published in Weale's Rndimentary Series. The following figures, copied from Garnicr's

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Such is a brief notice of the common method of boring Artesian wells. There is, however, considerable variation in the practice of different countries, and even of different districts, according to the geological nature of the place, and the views of the contractor. One of the simplest methods is that practised by the ingenious and industrious Chinese, who have from time immemorial been acquainted with the art of boring the earth for water or for salt brine. In the province of Szu-Tchhouan, on the borders of Thibet, occur a number of salt wells, accompanied by springs of inflammable gas; so that nature not only furnishes the brine, but also the fuel for evaporating the water and extracting the salt. There are several other wells of the same nature in the different districts of this department of Kia-TingFou, and in the other neighbouring districts, situated to the east of the great chain of mountains covered with perpetual snow, which traverses the eastern part of Szu-Tchhouan, from south to north. According to the report of M. Imbert, there are in the vicinity of the town of Ou-Thouang-Khiao several thousands of these salt wells in a space of ten leagues by five. Every person who is tolerably rich takes a few associates with him, and digs one or more wells. The expense of digging a well is from seven to eight thousand franes (280/. to 320/., a laTge sum in China), and the depth is commonly from 1,500 to 1,8Q0 French feet, and five or six inches in diameter. They arc usually bored in the solid rock. These people, who accomplish the most difficult undertakings with time and patience, begin by sinking vertically into the bed of earth, usually met with at the surface, a wooden pipe crowned with a hewn stone, perforated with a hole, which, like the pipe, has the same diameter as it is intended to give the well; that is, five or six inches. In this tube there is made to work a steel head of 300 or -100 lbs. weight. This steel is notched at the end, and is a little concave above and round beneath. A workman, by leaping upon the extremity of a lever, the other extremity of which is attached to the steel head, lifts it to the height of two feet, and lets it fall again by its own weight. Some pails of water arc thrown in from time to time, to assist the trituration of the substances. The spur or steel head is suspended by a cord, to which is attached a triangular piece of wood, and each time that the lever raises the cord, a second workman, seated near the tube, makes the triangle perform half a revolution, so that the steel head may fall in a different direction. At noon the second workman ascends upon the lever to take the place of his companion. At night two other men take their place. When three inches have been bored, the steel head is withdrawn by means of a pulley, with all the substances with which its upper concavity is loaded. By this mode of boring, the wells are perfectly vertical, and their inner surface highly polished. Beds of sand, coal, &c., are frequently met with. The operation then becomes more difficult, and is sometimes entirely frustrated; for these substances no longer offering an equal resistance, the well loses its vertically; but these cases are of rare occurrence. At other times the iron ring which bears the steel head breaks. When this accident happens at a certain depth, the Chinese know no other means of remedying it than to employ a second steel head to break the first, an operation which may take several months. When the rock is good, an advance of nearly two feet is made in twenty-four hours, so that it may take about three years to dig a well. For a further notice of these wells see Salt.

A method of boring, known in some parts of Europe as the Chinese system, is founded on the above method, Fig. 21g. and consists in suspending the borer by a (p) rope, which, when the tool is worked verP tically up and down, imparts by its torsion a sufficient circular motion. In Fig. 219, the tool is shown surrounded by an iron cylinder. The pounded earth or stone collects in the circular space between the tool and the cylinder, by which means they can be brought up to the surface. Different tools arc used for different strata, and the usual method of connecting the tool with a number of metal rods, as the work proceeds, is here dispensed with. The chief defect of this simple plan is that the bore-hole is apt to become crooked, so that it is often impossible to sink the pipes required to protect the hole.

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The great loss of time attending fhe plan of unscrewing and screwing, pulling up and letting dow-n the rods, is a defect in the common method of boring. An attempt was made to remedy this by an apparatus patented by Beart, in 1844. The rod connecting the boring tool with the workmen above is formed of a tube with water-tight joints: into this tube water is allowed to flow, an upward and a downward current being formed by allowing the water to flow in one direction in the tube, and in the other in the circular space around it. It was supposed that in this way the rubbish loosened by the tool would be brought up to the surface. A portion of the finer material might certainly be got rid of in this way, but not the great bulk of loosened matter; and it is also an objection to the plan, that a large quantity of water is required in places where the very act of boring would seem to indicate a scarcity of that article.

In addition to the examples of remarkable Artesian wells noticed under that head, we may here give a few details respecting the most remarkable work of the kind that has yet been executed. In a letter to the Times newspaper, dated 17th August, 1850, Dr. Granville notices the completion of the great Artesian salt spring at Kissingen. He states that on the 12th August last, "the curious spectacle was exhibited of a column of water, 4 inches in diameter, springing with a prodigious force out of the earth to the height of 58 feet, from a depth of l,878j feet, spreading out like a graceful palm-tree at its highest point, and forming the finest and most striking jet-d'eau of this kind ever beheld. The water, as clear as crystal, issues from the soil with a temperature of 66° F'ahr., charged with 3£ per cent. of pure salt, at the rate of 100 cubic feet per minute." Only one other such Artesian spring has been completed within the last two years, at Prcussich Munden, in which the salt water is drawn from a greater depth, but rises to an elevation of 15 feet only, and is not so intensely salt.

The saline valley in which Kissingen is seated stands at an elevation of 650 feet above the level of the Baltic Sea. The stratification of its rocks, from the surface downwards, as it has been revealed by the successive borings, is extremely simple. The boring implements first went through 1,240 feet of variegated sandstone; then through 350 feet of sandstone of the Vosges formation; next through I50feetof magnesian limestone (Zcchstein); and lastly through 138 J- feet of rock-salt, thus reaching a total depth, as before stated, of 1.878£ feet. In the latter, or rocksalt stratum (which is presumed to be 1,000 feet thick), a pure saline souree (Soole) is formed, by a solution of the rock-salt in water. This solution has been found to hold not less than 27i per cent. of salt; and as there is little likeUhood that they would be able to penetrate into the rock beyond 30 feet deeper, to that extent the perforation is to be pushed, and the well completed by the end of this year. At present the supply of water is at the rate of 100 cubic feet per minute, and the force with which this quantity is ejected to the height already stated is due to a source of almost entirely pure carbonic acid gas, which, having been met with at the depth of 1,680 feet from the surface, at (he junction of the gypsum and zeehstein, escaped with prodigious force into and out of the Artesian bore-hole, propelling the superincumbent column of water into the air, in the maimer above mentioned. In the course of the boring operations, two distinct salt wells were gone through at 222 and 1,240 feet depths, with the respective temperatures of 50° and 66° Fahr., and 1£ and 2£ per cent. of salt. It was under both these wells, at the depth of 1,680 feet, that the great carbonic acid gas stratum was first tapped. This stratum of gas would seem to be eqnally spread under and throughout the breadth of the valley, imparting its peculiarly piquant and pleasant character to the several mineral springs of this spa. The presence of so enormous a quantity of gas giving rise to an extraordinary commotion in the bore-hole, soon proved an impediment to the further extension of the latter. This induced Inspector Knorr to have recourse to a new and simple contrivance, by which he can arrest the flow of the gas into the Artesian bore, by compelling it to disperse itself through its subterranean recesses, whilst he proceeds downwards with his work of perforation. When the entire work shall have been completed, 3f cubic feet of brine per minute, free from iron and all other impurities, capable of yielding 50 lbs. of crystallized salt, will be conveyed to the boiling-house for crystallization>, carrying with it a temperature of 92° Fahr. But it is intended to limit the whole annual

produce of salt from this source to C,000,0001bs., which, at the current market price, will add to the revenue of the crown of Bavaria 300,000 florins, after deducting 60,000 florins for yearly expenses of work, fuel, and management. The whole cost of this work will amount to 80.000 florins (6,666/.). It was begun in the shaft of an old well, in 1832, from which time, and during a period of 11 years, 800 feet only were bored through the rocks, the operation being often interrupted, and even suspended, from a feeling of discouragement; but, in 1843, Inspector Joseph Knorr, confidently predicating an ultimately successful result, advised the government to resume operations, w-hieh have never since been interrupted, either by day or night, and are now about to be completed.

BORON is met with in nature combined with oxygen, forming boracic acid. To separate the oxygen, a portion of boracic acid is heated with potassinm in a tube; the oxygen partly combines with the potassium, forming potash, and that portion of the acid which is not decomposed, unites with the potash, forming borate of potash. The mixture is then placed in water, when the borate of potash dissolves, and the boron floats in the shape of a brown powder. Boron is of no importance in the useful arts; its chemical symbol is B.

Boracic acid is found in Thibet and in South America; but the principal supply in Europe is from the voleanic districts of Tuscany, called ]/tgoom, where jets of vapour, called sujjioni, and of boiling water, charged with boracic acid, are continually

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issuing from cracks m the ground. Before the manufacture of boracic acid from these sources was undertaken, the district was a positive nuisance, both from the foetid odour diffused around, and from the accidents which frequently occurred both to man and beast. "As you approach the lagoons," says Dr. Bowring, "the earth seems to pour out boiling wafer, as if from voleanoes of various sizes, in a variety of soib, but chiefly of chalk and sand. The heat in the immediate neighbourhood is intolerable, and you are drenched by the vapour, which impregnates the atmosphere with a strong and somewhat sulphureous smell. The whole scene is one of terrible violence and confusion:—the noisv outbreak of the boiling

element; the rugged and agitated surface; the volumes of vapour; the impregnated atmosphere; the rush of waters among bleak and solitary mountains. The ground, which burns and shakes beneath your feet, is covered with beautiful crystallizations of sulphur and other minerals; its character beneath the surface at Monte Ccrboli is that of a black marl, streaked with chalk, giving it at a short distance the appearance of variegated marble."

When the soil exhibits at any spot a high temperature, and vapours of sulphur ascend from it, or any earthquake is felt, a basin more or less deep, according to the locality, is dug there. A column of vapour sndtlenlv issues with considerable force from the earth; this is surrounded with a wooden chimney, in order to protect the workmen. A suitable form is given to the basin, aud the sides are lined with stone. The depth aud cireumference of such a basin must be in a certain relation to the foree of the column of vapour; for, when the depth and surface are too great, and the basin contains too much water, the passage of the vapour is too much opposed, and it often seeks another exit. These eruptions of vapour, however, are not very constant, for the voleano, after being active for several years, may disappear, and seek a new passage, at a distance of from 30 to 60 yards. From the uncertainty of these eruptions, the localities are dangerous to visit without a safe guide; for when the eruption ceases at a certain spot, it is uncertain at what point it will break out: it then frequently forms a subterranean lake near the surface, which breaks through with the weight of a man, and a very dangerous scalding may be the result.

When the walls of the lagoon are finished, the chimney is removed, and water from some souree is conducted into the basin, where it is heated to boiling by the ascending vapour, u, Fig. 220. The water, of which not much is evaporated, takes up from 1 to 1$, and rarely 2, per cent. of boracic acid. The lagoons are emptied every day, as the amount of boracic acid is not increased by remaining longer, and the solution is conducted from one basin into another, as from A to B, by means of the pipe o, until it reaches the reservoir E E, where it deposits its mud, &c., which, not containing any more boracic acid, is removed from time to time, the clear liquor occupying the upper level p, and the mud q. The clear water is then conducted into the evaporating-pans G G, which are heated by the voleanic steam. In the course of 62 hours, during which the liquor is passed from one pan to another by means of the syphon-tubes »'i, the solution is sufficiently concentrated, and is conveyed into woodeu cooling-vessels, A, Fig. 221, where it is

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left three days to cool, aud deposit crystals of boracic acid. The mother liquor is drawn off into channels B B, and returned to the clarifying reservoir, while the crystals of boracic acid, being first drained in baskets, c, arc dried in chambers, D r', heated by voleanic vapour. The crystals are purified by dissolving them in two and a half times their weight of boiling water, and crystallizing a second, or even a third time, if the acid be required very pure.

The dimensions of the lagoons vary from 100 feet in cireumference, and 7 feet deep, to 500 and 1,000 feet in cireumference, and 15 to 20 feet deep. The large ones enclose from 3 to 15 sources. The con

struction of these basins required considerable works; terraces had to be built, and hollows filled up, in order to keep the water at the proper level. Kivulets had to be turned out of their course, to prevent their influence on the basins.

In order to heat the cvaporating-pans, &c., those sourees are turned to account which are not suited to the construction of lagoons. The jets are snrrounded in the manner before described, and thence conveyed in subterranean stone passages beneath the evaporating-pans. Each series consists of 14, I8, and 26 pans, 1 foot deep, and 10 feet superficies. The vapour condensed in the passages flows off through an aperture, and the uncondensed vapour escapes through a chimney.

In the year 1846 there were 400 evaporating-pans in operation, each of 10 feet surface, besides which there were several others with diaphragms, arranged in rows, 300 feet in length, in which the water, constantly evaporating, flowed slowly through thedifferent divisions, until it was fit for the cooling vessels. Upwards of 1,200 lbs. of water are evaporated in the course of a day. Until the year 1827, wood was employed for heating the evaporating-pans; but since that time the economical method of heating by the voleanic steam has been adopted, by which a saving of about 10,000,000 franes has been effected. The production of boracic acid in 1846 amounted to 3,Q00,000 Tuscan pounds. It is stated, however, that the impurity of the acid increases every year, which is probably due to the progressive alteration of the strata, disintegrated by the currents of vapour, and the infiltrations of water. The first products contained from 90 to 92 per cent. of pure crystallized acid; but, according to M. Payen, they now contain from 18 to 25 per cent. of foreign matters.

The composition of boracic acid is

Oxygen 68.78

Boron 31.22

100.00

Boracic acid is much used in the manufacture of borax, and also in the manufacture of paste for artificial gems; it has also been used with success in the manufacture of enamel. ..

Borax is a compound salt, formed by the combination of boracic acid with soda. It is first mentioned in the writings of the alehemist Geber, in the tenth century. It has a sweetish taste, and dissolves in 12 parts of cold, or 2 parts of boiling water. It unites with metallic oxides, forming various coloured glasses: with oxide of chrome, it forms an emerald green; with oxide of cobalt, an intense blue; with oxide of copper, a pale green; with oxide of tin, an opal; with oxide of iron, bottle-green, and yellow; with oxide of manganese, a violet; with oxide of nickel, pale emerald-green. The white metallic oxides produce a colourless glass. Borax is very useful as a flux, both to the goldsmith, in soldering the precious metals, and to the brazier, in soldering copper and iron, as it prevents the metal of the flux from oxidizing, and eveu dissolves any oxide that may h/.w been formed.

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