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Is it not a sad thing to fall thus plumb into the

grave? well one minute, and dead the next. Collier.

of the channel.

The most experienced seamen plumbed the depth Swift. PLUMB ISLAND, an island in the Atlantic, near the coast of Massachusetts, between Newburyport and Ipswich; nine miles long, and one broad. Its south end is on the north of the entrance of Ipswich harbour, and its north end on the south of the entrance of Newburyport. Near the north end there are two lights. Several houses have been erected on this island by the Marine and Humane Society. There is also an elegant hotel about a mile south of the lights. A bridge has been built across Plumb Istand River, and an excellent road has been made from Newburyport to the island, a distance of three miles. This island is a place of much resort in the summer. Also, a small island near the northeast coast of Long Island, in the state of New York. It is annexed to Southold.

PLUMB LINE, among artificers, denotes a perpendicular to the horizon; so called, as being commonly extended by means of a plummet.

PLUMBAGO, in botany, lead-wort, a genus of the monogynia order, and pentandria class of plants. There are four species; the most remarkable are

1. P. Europæa. It grows naturally in the south of Europe, and has a perennial root striking deep into the ground. There are many slender channelled stalks, about three feet high, terminated by tufts of small funnel-shaped flowers, of a blue or white color. It is propagated by seeds, and by parting the roots.

2. P. Zeylonica grows naturally in both the Indies. The upper part of the stalk and empalement is covered with a glutinous juice, which catches the small flies that light upon it. It is too tender to thrive in the open air in this country.

PLUMBAGO, in chemistry and mineralogy, carburet of iron, graphite of Werner, and fercarbure of Hauy, a species of mineral carbon, of a dark iron gray or black color, occurring in masses in kidney-shaped lumps, and disseminated. It has a glistening metallic lustre; its fracture is small, somewhat curved, foliated, approaching to scaly, or granular uneven. It occurs generally in granular or scaly distinct concretions; takes a polish by cutting or rubbing; gives a dark lead-gray streak, and is unctuous to the feel, soft, and not very brittle. Spec. grav. 1·98 to 2:26. It does not flame when heated, nor can it by itself support combustion. After long exposure to a high heat in a muffle its carbon is burnt off, and its earthy and metallic part remains behind. If one part of plumbago, and two of very caustic dry alkaline, be heated in a retort with the pneumato-chemical apparatus, the alkaline becomes effervescent, hydrogen gas is obtained, and the plumbago disappears. This experiment proves that the small quantity of water contain in the

salt is decomposed, and that its oxygen, by con bining with the carbon of plumbago, forms the carbonic acid.

Scheele and Berthollet, consists of about ninety The purer kind of plumbago, according to per cent. of carbon and ten of iron. An impure kind from Pluffier afforded Vauquelin of twentythree carbon, two iron, thirty-seven alumine, thirty-eight silex.

Mr. Maculloch asserts that a certain portion of plumbago often found in pig-iron adds considerably to its toughness. On one occasion in particular he mentions that a cannon had been condemned for some fault in the bore, and it was found to be so exceedingly tough that no e of the men were able to break off a trunnion, as is the usual practice in these cases, when three or four blows of the sledge were commonly found sufficient for this purpose. I was particularly induced therefore,' says Mr. Maculloch, to examine this specimen, and was surprised to find that it not only contained a most unusual proportion of plumbago, but that this was in what I may call a disengaged state, for want of a better term. The plumbago was not only visible on breaking the metal, giving it the appearance of having been rubbed with powdered black lead, but the iron was capable of leaving its trace on paper. I have neither before nor since ever met with another example of this kind. The remaining guns of this lot, which must have been made of the same metal, went on service, and some of them are probably still existing. I have no doubt that they were the best that we received during the war; and it would have been very desirable to have discovered by what means this very uncommon specimen of gun-metal had been procured, as its toughness is a matter of such importance. It was from Mr. Walker's foundery. I do not pretend to account for this singular state of the iron; as, although the presence of plumbago is sufficient to affect the color of the metal, it is never, bating this instance, distinctly visible, as far as my experience goes. Yet, in gun-metal it is easy to conjecture its presence and proportion by the color of the fracture; which is darkest or most gray where it is most abundant. The trials which I have made also go to prove that the grayest metal is the toughest; although I know that many ironfounders consider that gun-metal may be too gray, and act on this principle in the assortment of the pigs for the reverberatory.'

Much of the attention of modern chemists has been excited by a curious apparent conversion of pig and cast iron into plumbago. It has been more particularly exhibited in the pipes in porter-breweries and calico-printing houses, and in those of gas-manufactories. The writer of this article has in his possession a portion of a pipe that was used for seventeen years and a half by one of these gas-houses, and that now exhibits every character of black-lead. The most remarkable quality of this is, that, on its first exposure to the air, its heat was sufficient to evaporate the moisture on its surface with rapidity, and increased till it became impossible to hold it. The following is another of many instances of the same description:

After captain Roe had invented the divingbell, he joined Sir Archibald Grant, a great speculator of that day in coal-mines and other matters, in an attempt to weigh the Florida, one of the Spanish Armada, which had foundered off the coast of Mull, near the entrance of Tobermory harbour. This attempt, which took place in 1740, was unsuccessful, as far as related to the ship; but some guns, both of brass and iron, were brought up. The former, whether they belonged to the Spanish vessel or not, had the mark of an English founder, R. and J. Philips, 1584, with a crown and E. R. on them. The iron guns were deeply corroded, and, on scraping them, it was said that they were found so hot that they could not be touched, and that they did not become cool till they had been two or three hours exposed to the air.

The astonishment of the Highlanders on finding guns still hot, after having been more than a century under water, may easily be imagined; and it is not surprising that the story was not believed and that not being believed, it was forgotten. This may afford us a useful hint on the subject of physical incredulity: since assuredly a fact thus nakedly stated, without a knowledge of the explanation here given, must have been pronounced impossible by every one, chemist or not. The blackest pig-metal appears to yield the greatest quantity of black lead, and in the most solid state. When the experiment is complete, the produce equals the iron in bulk, and is a solid mass, capable of being cut by a knife, even into pencils; but, it is of a much more coarse grain, or scaly granular texture, than any natural black lead that has occurred to

me.

To procure it in perfection, the acid should be very weak, and the operation is then necessarily very tedious. Acetous acid appears to be the best, and it is by this that it is produced in porter-backs, in the waste-pipes of breweries, and in calico printing-houses, where sour paste is employed. The process by water is insufferably tedious.

If the experiment is perfect, the black lead becomes hot on exposure to air, smoking while there is any moisture to be evaporated.

Thus black lead is an oxide of plumbago, or of carbon, if we choose to use this term for the presumed element. It is scarcely necessary to say that the metallic nature of the base of charcoal is proved by the same experiment; nor that iron is not a necessary ingredient in black lead. The best kinds, indeed, are those which contain least.

This experiment, and these conclusions, would be much more satisfactory, if we could produce the metal of black lead in its separate state. No method of doing that has yet occurred to any one; and it will probably be found a very difficult problem, as this is evidently a highly combustible substance. But chemistry does so much every day that once appeared hopeless, that we have no reason to despair.

Plumbago was formerly supposed absolutely infusible, but professor Selleman having succeeded in fusing and volatilising charcoal by Dr. Hare's Galvanic Deflagrator, applied the same

powerful instrument to plumbago, and obtained the following results :- From a piece,' says he, of very fine plumbago, from Carolina, I sawed small parallelopipeds, about one-eighth of an inch in diameter and from three-fourths of an inch to one inch and a quarter in length: these were sharpened at one end, and one of them was employed to point one pole of the deflagrator, while the other was terminated by prepared charcoal. The best were obtained when the plumbago was connected with the copper, and prepared charcoal with the zinc pole. The spark was vivid, and globules of melted plumbago could be discerned, even in the midst of the ignition, forming and formed upon the edges of the focus of heat. In this region also there was a bright scintillation, evidently owing to combustion, which went on where air had free access, but was prevented by the vapor of carbon, which occupied the highly luminous region of the focus, between the poles, and of the direct route between them. Just on and beyond the confines of the ignited portion of the plumbago there was formed a belt of a reddish-brown color, a quarter of an inch or more in diameter, which appeared to be owing to the iron, remaining from the combustion of the carbon of that part of the piece, and which, being now oxidized to a maximum, assumed the usual color of the peroxide of that metal.

In various trials, the globules were formed very abundantly on the edge of the focus, and, in several instances, were studded around so thickly as to resemble a string of beads, of which the largest were of the size of the smallest shot; others were merely visible to the naked eye, and others still were microscopic. No globule ever appeared on the point of the plumbago which had been in the focus of heat, but this point presented a hemispherical excavation, and the plumbago there had the appearance of black scoria or volcanic cinders. These were the general appearances at the copper pole occupied by the plumbago.

On the zinc pole, occupied by the prepared charcoal, there were very peculiar results. This pole was, in every instance, elongated towards the copper pole, and the black matter accumulated there presented every appearance of fusion, not into globules, but into a fibrous and striated form, like the half-flowing slag found on the upper currents of lava. It was evidently transferred, in the state of vapor, from the plumbago of the other pole, and had been formed by the carbon taken from the hemispherical cavity. It was so different from the melted charcoal, described in my former communications, that its origin from the plumbago could admit of no reasonable doubt. I am now to state other appearances, which have excited in my mind a very deep interest. On the end of the prepared charcoal, and occupying frequently an area of a quarter of an inch or more in diameter, were found numerous globules of perfectly melted matter, entirely spherical in their form, having a high vitreous lustre, and a great degree of beauty. Some of them, and generally they were those most remote from the focus, were of a jet black, like the most perfect obsidian; others were

brown, yellow, and topaz colored; others still were grayish-white, like pearl-stones, with the translucence and lustre of porcelain; and others still limpid like flint-glass, or, in some cases, like hyalite or precious opal, but without the iridescence of the latter. Few of the globules upon the zine pole were perfectly black, while very few of those on the copper pole were otherwise. In one instance, when I used some of the very pure English plumbago (believed to be from Borrowdale, white and transparent globules were forme I on the copper side.

I detached some of the globules, and, partly ing them in a handle of wood, tried their lassan 1 firmness; they bore strong pressure ot breaking, and easily scratched, not only +1-_lass, but window-glass, and even the hard en variety, which forms the aquafortis bottles.' Wale again repeating the experiments, professor Silliman obtained still finer results.

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The spheres of melted plumbago were in some instances so thickly arranged as to resemble scot lying side by side; in one case they com, letely covered the plumbago, in the part contigons to the point on the zine side, and wer without exception, white, like minute, deheate concretions of mammillary chalcedony. Vuong creat number there was not one of a r's color, except that, when detached by the fe, they exhibited slight shades of brown at place where they were united with the generi mass of plumbago. They appeared to me to be formed by the condensation of a white vi or, which, in all the experiments where an Active power was employed, I had observed to be exhaled between the poles, and partly to pass from the copper to the zine pole, and partly to rise vertically in an abundant fume like that of the oxide proceeding from the combustion of various metals. It seems possible that it is white volatilised carbon, giving origin, by its condensation, in a state of greater or less purity, to the gray, white, and perhaps to the limpid globules. I have already stated that the white fume mentioned above, appears when points of charcoal are used. I have found that this matter collects in considerable quantities a little out of the focus of heat around the zinc pole, and occasionally exhibits the appearance of a frit of white enamel, or looks a little like pumice stone: only it has the whiteness of porcelain, graduating, however, into light gray, and other shades, as it recedes from the intense heat. In a few instances I obtained upon the charcoal, when this substance terminated both poles, distinct, limpid spheres, and at other times they adhered to the frit like beads on a string. Had we not been encouraged by the remarkable facts already stated, it would appear very extravagant to ask whether this white frit and these limpid spheres could arise from carbon, volatilised in a white state even from charcoal itself, and condensed in a form analogous to the diamond. The rigorous and obvious experiments necessary to determine this question it is not now practicable for me to make; and I must, in the mean time, admit the possibility that alkaline and earthy impurities may have contributed to the result.'

In another experiment, professor Silliman

melted a piece of plumbago into two or three large limpid globules, and nothing remained of the original appearance of the plumbago but a small number of black points. Dr. Clarke says that the fusion of plumbago with the gas blowpipe was attended with a vivid scintillation. The surface was covered with a number of minute globules; some of which exhibited a limpid and highly transparent glass, others a glass of a brown hue; the larger globules being jet black and opake.

PLUMBERY is in part a practical application of hydraulics; it also embraces the casting and laying of sheet-lead as a covering on buildings. To the plumber is confided the pumpwork, as well as the making and forming reservoirs, large and small, for all the purposes of our domestic economy. To him, also, we are indebted for the water-closet, an apparatus of English invention, and unknown on the continent till the peace of Amiens allowed of its exportation.

This

The plumber chiefly works in lead. metal is known in the arts, from its durability, malleability, and many other properties, which renders it of the very highest importance.

As obtained from the mines, it is almost always combined with sulphur, and hence it is called a sulphuret. The operation of roasting the ore, or smelting, as it is called, to obtain the pure metal, consists:-1. In picking up the mineral to separate the unctuous, rich, or pure ore, and the stony matrix, and other impurities. 2. In pounding the picked ore under the stampers. 3. In washing the pulverised ore to carry off the matrix by the water. 4. In roasung the mineral in a reverberatory furnace, taking care to stir it, to facilitate the evaporation of the sulphur. When the surface begins to become of the consistence of paste, it is covered with charcoal, the mixture is shaken, the fire increased, and the lead then flows down on all sides to the bottom of the basin of the furnace, from which it is drawn off into moulds or patterns, prepared to receive it. The moulds are made so as to take a charge of metal equal to 154 lbs. ; these are called in commerce pigs, or pigs of lead, and are exported, and sold as such at the depots, by the lead merchants.

The plumbers use lead in sheets, and of these they have two kinds; one of which they call cast, and the other milled lead. The cast lead is used for the purpose of covering the flat roofs of terraces or buildings, forming gutters, lining reservoirs, &c. In architecture it is technically divided into 5, 51, 6, 61, 7, 71, 8, and 84 lbs. cast-lead, by which is understood that, to every foot superficial of such cast-lead, it is to contain these several weights of metal in each res pectively; so that an architect, when directing a plumber to cover or line a place with cast sheetlead, tells the workman that it is to be done with 6 or 7 lb. lead;' meaning by it that he expects each foot superficial of the metal to be equal in weight to Six, seven, or other number of pounds. The plumbers sometimes attempt deception in this arrangement, and particularly in work agreed for by contract, by putting down a liiter metal than the one they have engaged to

do. The writer of this article has often had occasion to interfere in such attempts, and has had the whole of such lead removed, not finding it adequate in weight per foot to that which was contracted for.

Every plumber, who conducts business to any extent, casts his sheet-lead at home; this he does from the pigs, or from old metal which he may have taken in exchange. The ductility of lead renders it easy to be run. They provide a copper, well fixed in masonry, and placed at one end of their casting-shop, and near to the mould or casting-table. The casting-table is generally in its form a parallelogram, varying in its size from six feet in width to eighteen or more feet in length. It is raised from the ground as high as to be about six or seven inches below the top of the copper which contains the metal, and stands on strongly framed legs, so as to be very steady and firm. The top of the table is lined by deal boarding laid very even and firm, and it has a rim projecting upwards, four or five inches, all round. At the end of the table, nearest to the copper in which is the heated lead, is adapted a box equal in length to the width of the table; at the bottom of this is a long horizontal slit, from which the heated metal is to issue when it is to be cast into sheets. This box moves upon rollers along the edges of the projecting rim of the table, and is set in motion by ropes and pulleys fixed to beams over the table. As soon as the metal is found to be adequately heated, every thing is made ready for casting it on the table, the bottom of which is then covered by a stratum of dry and clean sand, and a rake is applied to smooth it regularly all over the surface. When this is done the box is brought close up to the copper. It must be observed that these boxes are made, in their size, equal to the containing of as much of the melted lead as will cast the whole of the sheet at the same time, and the slit in the bottom is adjusted so as to let as much, and no more, out, during its progress along the table, as will be sufficient to cover it completely of the thickness and weight per foot required. When the box has dispersed its contents upon the table, it is suffered to cool and congeal, when it is rolled up and removed away, and other sheets are made till all the melted metal in the copper be cast. The sheets so formed are rolled up and weighed, as it is by weight the public are charged for sheet-lead.

The other kind of sheet-lead made use of by plumbers, called in the trade milled lead, is not manufactured at home. This they purchase of the lead merchant, as it is east and prepared commonly at the ore and roasting furnaces. Such kind of lead is very thin, and commonly there is not more than four pounds of metal to the foot superficial. It is used by architects for the covering only of the hips and ridges of roofs of buildings. It is by no means adapted to gutters or terraces, or, in fact, to any part of a building much exposed either to great wear and tear, or the effects of the sun, as it expands and cracks by the latter, and is soon worn away by exposure. It is laminated in sheets about the same size as has been described for cast sheetlead; and, in the operation of making, a lami

nating-roller is used, or a flatting-mill, which reduces it to the state in which it is seen in commerce.

Solder is used by the plumber for the purpose of securing the joints of leaden work, in cases in which a lap or roll-joint cannot be employed. It is a general rule with respect to solder, that it should a.ways be easier of fusion than the metal intended to be soldered by it. Next to this, care must be taken that the solder be as far as it is possible of the same color with the metal intended to be soldered. Technically, the soft solder is that which the plumber makes use of, by reason of its melting easily. This solder is composed of tin and lead, in equal parts, fused together; after which it is run into moulds in shape not unlike a common gridiron. In this state it is sold by the pound by the manufacturer. In the operation of soldering, the surfaces of the metal intended to be joined are scraped and rendered very clean, they are then brought close up to each other, and, to secure them, they are held by one plumber while another lays a

little resin or borax about the joint. This is done to defend the metal, while soldering, from oxidation. The heated solder is then brought in a ladle and poured on the joint to be soldered, and is smoothed and finished by rubbing it about with a heated grozing-iron, and, when complete, it is filed or scraped off, and made even with the joint and contiguous surface of the lead.

The plumber has no need of great variety of working tools, as the ductility of the metal he works in does not require them, and what he may require are generally supplied by the master tradesman. They consist of an iron hammer made rather heavier than they usually are seen, having a short but thick handle. Two or three different sized wooden mallets, and a dressing and flatting-tool. This instrument is made of beechen wood, commonly about eighteen inches long, and two inches and a half square, planed quite smooth on one side, and rounded into an arch on the other, or upper side. One of its ends is tapered and rounded to make it convenient to be held in the hand of the workman. With this tool the plumber stretches out and flattens all the sheet-lead, as well as dresses it into the shape it may be wanted in the various purposes to which such lead is applied, using first the flat side of this tool, and then the round side, as may be required. They have also a jack and trying-plane, similar to the same kind of tools used by carpenters. These tools consist of a piece of beechen wood, that for the former about sixteen inches, and for the latter twentytwo inches long, in each of which a flat iron of sharpened steel is fitted, and held to its work by wooden wedges adapted to mortises made at the distance of about one-third from the foreend of each plane. At the opposite end is formed a handle, by which the planes are worked. With such tools plumbers plane straight the edges of their sheet-lead, when it is required to present a very regular and correct line, as it is frequently wanted to do in architecture. They are provided also with a line and roller, called a chalk-line; with this they line out all the lead into the differ

ent widths it may be wanted. Their cutting tools embrace chisels and gouges of different sizes, as well as several cutting-knives. These latter are used for the purpose of accurately cutting the sheet-lead into the strips and pieces to the division marked by the chalk-line which has been drawn on the lead. They have files of different sizes, which they use in manufacturing of cistern leads to pipes, pump-work, &c.

For soldering, they keep a variety of different sized grozing-irons; these are commonly about twelve inches long, and tapered at both ends, the handle-end turned quite round to allow of its being held firmly in the hand while in use. The opposite ends of which are made spherical, and some of them are of a spindle-shape, and of a size in proportion to the soldering to be done with them. These irons are heated to redness when used. Their iron ladles are of three or four sizes, and used for the purpose of heating the solder.

A plumber's measuring rule is of two feet in length, divided into three parts, each of which is eight inches long. Two of its legs are of boxwood, and duodecimally divided, and a third of a piece of slow-tempered steel; this is attached to one of the box legs by a pivot, on which it turns, and, the same legs being grooved out on its side, it receives the steel leg, when not in use, in this groove. The plumber finds a rule of this description very convenient, inasmuch as he can pass the steel leg of his rule into places he may have to examine, which he could not readily get any thing else to enter: it also answers the purpose occasionally of removing the oxide or any other matter from off his heated metal. A plumber's rule, by being so made, is constantly in use in one way or another.

Scales and weights are also very essential, as nothing done by the plumber is chargeable till it be weighed. He is also supplied with centrebits of all sizes, and a stock to work them in, for the making perforations in lead or wood, where he may have occasion to insert pipes, &c., &c. The compasses he uses occasionally to strike out any circular portion of lead wanted to line or cover figures of that description.

required than the adherence of the lead by being closely hammered together, and down upon the flat: indeed all fastening to the sheet lead, exposed to heat and cold, ought to be avoided, as it expands and shrinks by such vicissitudes, and if secured so as to prevent these from spontaneously affecting it, it will be cracked and dilapidated quickly. When rolls are not used, which is sometimes the case from their being found inconvenient by their projection, seams, as they are called, are employed, and consist in simply bending the two edges of the lead which approach to each other up and again over one another, and then dressing them down close to the flat throughout their whole length. This plan is by no means equal to the one by the roll, either for neatness or security. Soldering the joints is sometimes had recourse to for such kind of work, but it is a very bad way, and no good plumber would recommend it, as lead so fixed will be cracked and leak like a sieve, after having been exposed to one summer's sun. Leaden-flats, as well as gutters, require to be laid with a current to keep them dry. The rule for forming of which consists in giving a fall from back to front, or in the way in which it is determined that the sheets of lead are to be laid. A quarter of an inch to the foot run is a sufficient fall for lead, that is, if the sheets be twenty feet long, and hence they will require to be laid five inches higher at one end than at the other. This inclination, or, as it is called, giving a current, is generally apportioned and determined on by the carpenter and plumber previously to the laying of the lead, while the former's part of the business is doing.

Flashings, as they are called, are pieces commonly of milled-lead about eight or nine inches wide, and fixed all round the extreme edges of a flat or gutter, in which lead has been used. If a wall of brick-work surround it, it is passed into the joint between the bricks and its other edge, dressed over that of the edge of the lead in the flat or gutter, and, when no joint can be found to receive its upper edge; it is then fastened by wall-hooks, and its other edge dressed down as before.

Drips in flats or gutters consist in raising one part above another, and dressing the lead as has been described for covering the rolls. They are had recourse to when the lengths of the gutter or flat exceed that of the length of the sheet, or sometimes for convenience; they are also an expedient to avoid joining the lead by soldering it.

Of laying sheet-lead.--The method usually adopted consists, if it be for terraces or flats, of covering such places with a bottom as even as possible, either by boarding or plastering; if by the former, observing to have the boards thick enough to prevent their warping and twisting upwards, as, when this is not attended to, the lead-work is soon cracked and becomes very un- The pipes used by the plumber are of various sightly. The sheets of lead not being more than sizes as well as descriptions. All the smaller about six feet in width makes it necessary to sizes are called by their calibre or bore, thus, have joints when a large surface is to be covered;,, 1, 11, 1, and 2-inch pipe. They originally these joints the plumber manages in various ways to prevent their leaking. The best way is by forming what are called rolls: a roll consists of a piece of wood of about two inches square, planed rounding on its upper side; these are fastened under the joints of the lead between the edges of the two sheets which meet together, one of which is dressed up over the roll on the inside, and the other over both of them on the outside, by which means the water is prevented from percolating the flat. No other fastening is

used to be cast by a core of wood of these respective diameters, but they are now all made by a machine worked by steam, which furnishes a neater article of almost any length, and considerably more cheap than heretofore. All those pipes, from to 14-inch calibre, are charged by the foot run, and those above that size by the hundred weight. The rain-water pipes attached to the outside of buildings, for the purpose of conveying off the superfluous water from the roofs of them, are called by the plumb

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