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vented by the above-named person, whereby the multiplication and division of large nunibers are much facilitated.

As to the Construction of Neper's Rods: suppose the common table of multiplication to be made upon a plate of metal, ivory, or paste-board, and then conceive the several columns (standing downwards from the digits on the head) to be cut asunder; and these are what we call Neper's rods for multiplication, But then there must be a good number of each; for as many times as any figure is in the multiplicand, so many rods of that species (i. e. with that figure on the top of it) must we have; though six rods of each species will be sufficient for any example in common affairs: there must also be as many rods of O's.

But before we explain the way of using these rods, there is another thing to be known, riz. that the figures on every rod are written in an order different from that in the table. Thus, the little square space, or division, in which the several products of every column are written, is divided into two parts by a line across, from the upper angle on the right to the lower on the left; and if the product is a digit, it is set in the lower division; if it has two places, the first is set in the lower, and the second in the upper division; but the spaces on the top are not divided; also there is a rod of digits, not divided, which is called the index rod, and of this we need but one single rod.

Multiplication by Neper's Rods. First lay down the index rod; then on the right of it set a rod, whose top is the figure in the highest place of the multiplicand: next to this again, set the rod whose top is the next figure of the multiplicand; and so on in order, to the first figure. Then is your multiplicand tabulated for all the nine digits; for in the same line of squares standing against every figure of the index-rod, you have the product of that figure, and therefore you have no more to do but to transfer the products and sum them. But in taking out these products from the rods, the order in which the figures stand obliges you to a very easy and small addition: thus, begin to take out the figure in the lower part, or unit's place, of the square of the first rod on the right: add the figure in the upper part of this rod to that in the lower part of the next, and so on, which may be done as fast as you can look on them. To make this practice as clear as possible, take the following example.

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To make the use of the rods yet more regular and easy; they are kept in a flat, square box, whose breadth is that of ten rods, and the length that of one rod, as thick as to hold six (or as many as you please) the capacity of the box being divided into ten cells, for the different species of rods. When the rods are put up in the box, (each species in its own cell distinguished by the first figure of the rod set before it on the face of the box near the top) as much of every rod stands withont the box as shews the first figure of that rod; also upon one of the flat sides without and near the edge, upon the left hand, the index-rod is fixed: and along the foot there is a small ledge, so that the rods, when ap plied, are laid upon this side, and supported by the ledge, which makes the practice very easy; but in case the multiplicand should have more than nine places, that upper face of the box may be made broader. Some make the rods with four different faces, and figures on each for different purposes.

Division by Neper's Rods. First tabulate your divisor; then you have it multiplied by all the digits, out of which you may choose such convenient divisors as will be next less to the figures in the dividend, and write the index answering in the quotient, and so continually, till the work is done. Thus 2,179,788, divided by 6,123, gives in the quotient 356.

Having tabulated the divisor, 6,123, you see that 6,123 cannot be had in 2,179; therefore take five places, and on the rods find a number that is equal, or next less to 21,797, which is 18,369; that is, three times the divisor, wherefore set 3 in the quotient, and subtract 18,369 from the figures above, and there will remain 3,428; to which add 8, the next figure of the dividend, and seek again on the rods for it, or the next less, which you will find to be five times; there. fore set 5 in the quotient, and subtract 30615 from 34,228, and there will remain 3,673, to which add 8, the last figure in the dividend, and finding it to be just six times the divisor, set 6 in the quotient,

6123) 2179788 (356

18369

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30615

36738

36758

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NEPETA, in botany, catmint, a genus of the Didynamia Gymnospermia class and order. Natural order of Verticillatæ. Labiatæ, Jussien. Essential character: corolla, lower lip with an intermediate segment, crenate; throat reflex at the edge; stamina approximating. There are twenty species, among which is the N. cataria, common catmint; it has a perennial root, and many branching stalks, about two feet in height, upright, pubescent; leaves of a velvet-like softness, wrinkled, ash-colour. ed; spikes, composed of interrupted whorls, terminate the stem; flowers sub-sessile; calyx downy, with green ribs; corolla white; the whole plant has a strong scent, between mint and pennyroyal; is is called catmint, because cats are very fond of it, especially when it is withered, when they will roll themselves on it, tear it to pieces, and chew it with pleasure. It is a native of most parts of Europe, on banks and hedges, chiefly in a calcareous soil, flowering from July to September.

NEPHELIUM, in botany, a genus of the Monoecia Pentandria class and order, Natural order of Tricoccæ. Corymbiferæ, Jussieu. Essential character: male, calyx five-toothed; corolla none: female, calyx four-cleft; corolla none; germs two, with two styles to each; drupes two, muricated, one-seeded. There is but one species, riz. N. lappaceum, a native of the East Indies.

NEPHRITE, in mineralogy, a species of the Talc genus; it is also called jade, or jade-stone. It was formerly celebrated for its medical virtues. It is of a dark leekgreen colour, verging to blue. It occurs massive in detached rounded pieces. The smooth external surface is glimmering with an oily lustre; internally it is dull, except when mixed with fibres. of asbestos and scales talc. The specific gravity is about 3. There are two sub-species: the common, and axe-stone: the former is somewhat brittle, takes a good polish, and is cut into handles for knives, &c.; the latter is made into hatchets by the natives of New Zealand. Nephrite is found in Egypt, China, America, the islands in the

Pacific Ocean, and in the Siberian mountains, sometimes adhering to rocks, and sometimes in detached round pieces. It is highly prized by the Hindoos and Chinese, by whom it is made into talismans and idols, and by the Turks, who form it into sword and dagger handies.

NEPHRITIC, something that relates to the kidneys.

NEREIS, in natural history, a genus of the Vermes Mollusca class and order. Body long, creeping, with numerous lateral peduncles or feet on each side; feelers simple, two or four eyes. There are about thirty species, in separate divisions, riz. A. Mouth furnished with a claw or forceps. B. Mouth furnished with a proboscis. C. Mouth furnished with a tube. N. noctiluca, body blue-green, with twenty-three segments, hardly visible to the naked eye. These are found in most seas, and are the animals that frequently illuminate the wa ter, making it appear as if on fire. They are extremely minute, pellucid, and highly phosphorus, giving an uncommonly lucid splendor to the waves in the evening. By their extreme numbers and smallness, they easily elude observation, but may be detected by passing a small quantity of water through blotting paper.

NERITA, in natural history, a genus of the Vermes Testacea class and order. Animal a limax ; shell univalve, spiral, gibbous, flattish at bottom; aperture semi-orbicnlar or semi-lunar; pillar-lip transversely truncate, flattish. There are nearly eighty species, divided into distinct sections, riz. A. Umbilicate. B. Imperforate, with the lips toothless. C. Imperforate, with the lips toothed. N. fluviatilis, with only two spires; brittle, dusky, marked with white spots. It is not half the size of a pea, and inhabits rivers and standing waters.

NERIUM, in botany, oleander, a genus of the Pentandria Monogynia class and order. Natural order of Contortæ, Apocineæ, Jussieu. Essential character: contorted; corolla with the tube terminated by a lacerated crown; follicles two, erect. There are nine species: these are beautiful evergreen shrubs or trees, upright and branching; leaves opposite, or by threes in a sort of whorl; flowers in clusters, or corymbs, from the ends of the stem and branches. They are chiefly natives of the East Indies.

NERTERIA, in botany, a genus of the Tetrandria Digynia class and order. Essential character: corolla funnel-form, four

cleft, superior; berry two-celled; seeds solitary. There is but one species, viz. N. depressa, found in New Granada.

graphy, an eminent chemist, was born in 1683, at Zuilichau, in the duchy of Crossen, in Brandenburg, of which place his father was a burgher and apothecary. He was brought up to his father's profession, and in 1705 went to Berlin, where he engaged in the service of the King of Prussia. After

NERVES, are cylindrical whitish parts, usually fibrose in their structure; or composed of clusters of filaments, arising from the brain, or rather from its medulla oblongata within the skull, and from the spi-having accompanied him in his journeys for nal marrow, and running from thence to every part of the body. See ANATOMY. NET, a device for catching fish and fowl. The taking fowls by nets is the readiest and most advantageous of all others where numbers are to be taken. The making the nets is very easy, and what every true sportsman ought to be able to do for himself. All the necessary tools are wooden needles, of which there should be several of different sizes, some round and others flat: a pair of round-pointed and flat scissars, and a wheel to wind off the thread. The pack thread is to be of different strength and thickness, according to the sort of birds to be taken; and the general size of the meshes, if not for very small birds, is two inches from point to point. The nets should neither be made too deep nor too long, for they are then difficult to manage; and they must be verged on each side with twisted thread. The natural colour of the thread is too bright and pale, and is therefore in many cases to be altered. The most usual colour is the russet, which is to be obtained by plunging the net after it is made into a tanner's pit, and letting it lie there till it be sufficiently tinged: this is of a double service to the net, since it preserves the thread as well as alters the colour. The green colour is given by chopping some green wheat and boiling it in water, and then soaking the net in this green tincture. The yellow colour is given in the same manner with the decoction of celandine, which gives a pale straw colour, which is the colour of stubble in the harvest time. The brown nets are to be used on ploughed lands, the green on grass grounds, and the yellow on stubble lands.

some years, he was allowed to study at the university of Halle, and was then sent at the King's expence to travel for improvement in chemical knowledge. In 1711 he visited the German mines, and thence passed into Holland, where he attended the lectures of the illustrious Boerhaave. Thence he went to England, where the news of the death of his sovereign, in 1713, somewhat deranged his plans. He again visited Holland, and in 1716 accompanied George I. King of England, to Hanover. On repairing to Berlin, he obtained the friendship of Stahl, physician to Frederick-William, who procured an order for him to resume his travels at the expence of the court. He visited France and Italy, every where increasing his stock of scientific knowledge, and forming connections with men of eminence. Upon his return to Berlin he was appointed court-apothecary; and when the king, in 1723, established a college of medicine and surgery in his capital, Neumann was nominated to the chair of chemistry. He received the degree of M. D. from Halle in 1727, and in that year travelled through Silesia and Moravia to Vienna, returning by Bohemia and the mining country of Saxony. His reputation now extended to the different countries of Europe, and he was elected a member of the Royal Society of London, of the Imperial Academy Naturæ Curiosorum, and of the Institute of Bologna. In 1734 he made a tour to the New Marche and Pomerania, where he discovered the true origin of Ostescolla. He became dean of the college of Berlin in 1736, and died in that city in 1737. The works published by Dr. Neumann in his life-time, consist chiefly of dissertations in the Latin language, inserted in the "Philosophia! Transactions of London," the "Ephemerides Acad. Naturæ Curiosorum," and the "Miscellanea Berolinensia, and of others in the German language published separately. After his death two different copies of his "Chemical Lectures" were given to the public; one, in two editions, at Berlin and Dresden, from notes taken by one of his NETTLE. See URTICA pupils, intermixed with compilations from NEUMANN (Gaspar, M. D.) in bio- different authors; the other by the book

NETTINGS, in a ship, a sort of grates made of small ropes, seized together with rope-yarn or twine, and fixed on the quarters and in the tops; they are sometimes stretched upon the ledges from the wastetrees to the roof trees, from the top of the forecastle to the poop; and sometimes are laid in the waste of a ship to serve instead of gratings.

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*llers of the Orphan Hospital of Zulichan, from papers in Neumann's own hand-writing: of this there have been two impressions, the first in a large form, the second in an abridg. ment; which last, however, consists of two volumes quarto. From this Dr. Lewis has made an excellent English translation in two volumes, octavo, still further abridged, but better methodized, and enriched with notes. "Neumann's Lectures," says Dr. Lewis, " are a valuable magazine of chemical knowledge. The author, biassed by no theory, and attached to no opinions, bas enquired by experiment into the properties and uses of the most considerable natural and artificial productions, and the prepara tion of the principal commodities which depend on chemistry; and seems to have candidly, and without reserve, communicated all he discovered." Such a work must retain its value, notwithstanding the great modern changes in chemical theory.

NEURADA, in botany, a genus of the Decandria Decagynia class and order. Natural order of Succulenta. Rosacea, Jussien. Essential character: calyx five-parted; petals five; capsule inferior, ten-celled, ten-seeded, prickly. There is but one species; riz. N. procumbens, an annual plant; native of Egypt, Arabia, and Numidia.

NEUROPTERA, in natural history, the name of the fourth order of insects according to the Linnæan system, and so called on account of the nerves and veins disposed in their wings. The insects of this order have four wings: all of them membranaceous, reticulate: tail unarmed. There are seven genera, viz.

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continue to add the soda, the mixtoré gradually acquires alkaline properties, converting vegetable blues to green, and manifesting an urinous taste. These properties become stronger and stronger the greater the quantity of the soda is which is added. Thus it appears that when sulphuric acid and soda are mixed together, the properties either of the one or the other preponderate according to the proportions of each; but that there are certain proportions, according to which, when they are combined, they mutually destroy or disguise the properties of each other, so that neither predominates, or rather so that both disappear. When substances thus mutually disguise each other's properties, they are said to neutralize one another. This property is commen to a great number of bodies; but it manifests itself most strongly, and was first observed in the acids, alkalies, and earths. Hence the salts which are combinations of these different bodies received long ago the name of neutral salts.

NEWTON (SIR ISAAC), in biography, one of the greatest philosophers and mathematicians the world has produced, was born at Woolstrop, in Lincolnshire, on Christmas Day, 1642. He was descended from the eldest branch of the family of Sir John Newton, Bart. who were Lords of the manor of Woolstrop, and had been possessed of the estate for about two centuries before; to which they had removed from Westley, in the same county; but originally they came from the town of Newton, in

Lancashire.

Other accounts say, probably with more truth, that he was the only child of Mr. John Newton, of Colesworth, near Grantham, in Lincolnshire, who had there an estate of about 120l. a year, which he kept in his own hands. His mother was of the ancient and opulent family of the Ayscoughs, or Askews, of the same county. Our author

NEUTRAL salts. See next article; also losing his father while he was very young, SALTS.

NEUTRALIZATION, in chemistry, may be thus explained: if we take a given quantity of sulphuric acid diluted with water, and add it slowly to the solution of soda by little at a time, and examine the mixture after every addition, we shall find that for a considerable time it will exhibit the properties of an acid, reddening vegetable blues, and having a taste perceptibly sour: but these acid properties gradually diminish after every addition of the alkaline solution, and at last disappear altogether. If we still

the care of his education devolved on his mother, who, though she married again, did not neglect to improve by a liberal education the promising genius that was observed in her son. At twelve years of age, by the advice of his maternal uncle, he was sent to the grammar school at Grantham, where he made a good proficiency in the languages, and laid the foundation of his future studies. Even here was observed in him a strong inclination to figures and philosophical subjects. One trait of this early disposition is told of him: he had then a rude method of

measuring the force of the wind blowing against him, by observing how much farther he could leap in the direction of the wind, or blowing on his back, than he could leap the contrary way, or opposed to the wind; an early mark of his original infantine genius.

After a few years spent here, his mother took him home; intending, as she had no other child, to have the pleasure of his company; and that, after the manner of his father before him, he should occupy his own

estate.

But instead of attending to the markets, or the business of the farm, he was always studying and poring over his books, even by stealth, from his mother's knowledge. On one of these occasions his uncle discovered him one day in a hay-loft at Grantham, whither he had been sent to the market, working a mathematical problem; and having otherwise observed the boy's mind to be uncommonly bent upon learning, he prevailed upon his sister to part with him; and he was accordingly sent, in 1660, to Trinity College, in Cambridge, where his uncle, having himself been a member of it, had still many friends. Isaac was soon taken notice of by Dr. Barrow, who was at this time appointed the first Lucasian professor of mathematics; and observing his bright genius, contracted a great friend ship for him. At his commencement, Euclid was first put into his hands, as usual; but that author was soon dismissed, seeming to him too plain and easy, and unworthy of taking up his time. He understood him almost before he read him ; and a cast of his eye upon the contents of his theorems, was sufficient to make him master of them; and as the analytical method of Des Cartes was then much in vogue, he particularly applied to it, and Kepler's optics, &c. making several improvements on them, which he entered upon the margins of the books as he went on, as his custom was in studying any author.

Thus he was employed till the year 1664, when he opened a way into his new method of Fluxions and Infinite Series; and the same year took the degree of Bachelor of Arts. In the mean time observing, that the mathematicians were much engaged in the business of improving telescopes, by grind. ing glasses into one of the figures made by the three sections of a cone, upon the principles then generally entertained, that light was homogeneous, he set himself to grinding of optic glasses, of other figures than spherical, having as yet no distrust of the ho

mogenous nature of light; but not hitting presently upon any thing in this attempt to satisfy his mind, he procured a glass prism, that he might try the celebrated phenomena of colours, discovered by Grimaldi not long before. He was much pleased at first with the vivid brightness of the colours produced by this experiment; but after a while, considering them in a philosophical way, with that circumspection which was natural to him, he was surprised to see them in an oblong form, which, according to the received rule of refractions, ought to be circular. At first he thought the irregularity might possibly be no more than accidental; but this was what he could not leave without further enquiry: accordingly he soon invented an infallible method of deciding the question, and the result was his New Theory of Light and Colours.

However, the theory alone, unexpected and surprising as it was, did not satisfy him; he rather considered the proper use that might be made of it for improving telescopes, which was his first design. To this end, having now discovered that light was not homogeneous, but an heterogeneous mixture of differently refrangible rays, he computed the errors arising from this dif ferent refrangibility; and, finding them to exceed some hundreds of times those occasioned by the circular figure of the glasses, he threw aside his glass works, and began to consider the subject with precision. He was now sensible that optical instruments might be brought to any degree of perfection desired, in case there could be found a reflecting substance which could polish as finely as glass, and reflect as much light as glass transmits, and the art of giving it a parabolical figure he also attained; but these at first seemed to him very great difficulties; nay, he thought them almost insuperable, when he further considered, that every irregula rity in a reflecting superficies makes the rays stray five or six times more from their due course, than the like irregularities in a refracting one.

Amidst these speculations, he was forced from Cambridge, in 1665, by the plague; and it was more than two years before he made any further progress in the subject. However, he was far from passing his time idly in the country; on the contrary, it was here, at this time, that he first started the hint that gave rise to the system of the world, which is the main subject of the Principia. In his retirement he was sitting alone in a garden, when some apples falling

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