Needles make a very considerable article in commerce, though there is scarce any commodity cheaper, the consumption of them being almost incredible.—The sizes are from no. 1, the largest, to no. 25, the smallest. In the manufacture of needles, German and Hungarian steel are of most repute.
In the making of them, the first thing is to pass the steel through a coal fire, and under a hammer, to bring it out of its square figure into a cylindrical one. This done, it is drawn through a large hole of a wire-drawing iron, and returned into the fire, and drawn through a second hole of the iron smaller than the first; and thus successively from hole to hole, till it has acquired the degree of fineness required for that species of needles; observing every time it is to be drawn, that it be greased over with lard, to render it more manageable. The steel thus reduced to a fine wire, is cut in pieces of the length of the needles intended. These pieces are flattened at one end on the anvil, in order to form the head and eye: they are then put into the fire, to soften them farther; and thence taken out and pierced at each extreme of the flat part on the anvil, by force of a puncheon of well-tempered steel, and laid on a leaden block to bring out, with another puncheon, the little piece of steel remaining in the eye. The corners are then filed off the square of the heads, and a little cavity filed on each side of the flat of the head; this done, the point is formed with a file, and the whole filed over: they are then laid to heat red hot on a long narrow iron, crooked at one end, in a charcoal fire; and when taken out thence, are thrown into a bath of cold water to harden. On this operation a good deal depends; too much heat burns them, and too little leaves them soft; the medium is learned by experience. When they are thus hardened, they are laid in an iron shovel on a fire more or less brisk in proportion to the thickness of the needles; taking care to move them from time to time. This serves to temper them, and take off their brittleness; great care here too must be taken of the degree of heat: They are then straightened one after another with the hammer, the coldness of the water used in hardening them having twisted the greatest part of them.
The next process is the polishing them. To do this, they take 12,000 or 15,000 needles, and range them in little heaps against each other on a piece of new buckram sprinkled with emery-dust. The needles thus disposed, emery-dust is thrown over them, which is again sprinkled with oil of olives; at last the whole is made up into a roll, well bound at both ends. This roll is then laid on a polishing table, and over it a thick plank loaded with stones, which two men work backwards and forwards a day and a half, or two days, successively; by which means the roll thus continually agitated by the weight and motion of the plank over it, the needles withinside being rubbed against each other with oil and emery, are infinitely polished. After polishing, they are taken out, and the filth washed off them with hot water and soap: they are then wiped in hot bran, a little moistened, placed with the needles in a round box, suspended in the air by a cord, which is kept stirring till the bran and needles be dry. The needles thus wiped in two or three different brans, are taken out and put in wooden vessels, to have the good separated from those whose points or eyes have been broken either in polishing or wiping; the points are then all turned the same way, and smoothed with an emery stone turned with a wheel. This operation finishes them, and there remains nothing but to make them into packets of 250 each. Needles were first made in England by a native of India in 1545; but the art was lost at his death: it was, however, recovered by Christopher Greening in 1560, who was settled with his three children, Elizabeth, John, and Thomas, by Mr Damar, ancestor of the present lord Milton, at Long Crendon in Bucks, where the manufactory has been carried on from that time to this present day.
Dipping-Needle, or Inclinatory Needle, a magnetic needle, so hung, as that, instead of playing horizontally, and pointing out north and south, one end dips, or inclines to the horizon, and the other points to a certain degree of elevation above it.
The dipping-needle was invented in the year 1575 by one Robert Norman a compass-maker at Wapping. The occasion of the discovery, according to his own account, was, that it being his custom to finish and hang the needles of his compasses before he touched them, he always found, that immediately after the touch, the north-point would bend or incline downward, under the horizon; insomuch that, to balance the needle again, he was always forced to put a piece of wax on the south end as a counterpoise. The constancy of this effect led him at length to observe the precise quantity of the dip, or to measure the greatest angle which the needle would make with the horizon; and this at London he found to be 71° 50′. In 1723 Mr Graham made a great many observations on the dipping-needle, and found the angle to be between 71° and 75° degrees. Mr Nairne, in 1722, found it to be somewhat above 72°. It is not certain whether the dip varies, as well as the horizontal direction, in the same place. The trifling difference between Mr Norman and Mr Nairne would lead us to imagine that the dip was unalterable; but Mr Graham, who was a very accurate observer, makes the difference more considerable. It is certain, however, from a great number of experiments and observations, that the dip is variable in different latitudes, and that it increases in going northwards. It appears from a table of observations made with the marine dipping-needle in a voyage... voyage towards the north pole in 1733, that in lat. 60° 18', the dip was 75°; and in lat. 70° 45', it was 77° 52'; in lat. 80° 12', it was 81° 52'; and in lat. 80° 27', it was 82° 2½'.
Several authors have endeavoured to apply this discovery of the dip to the finding of the latitude; and Mr Bond attempted to apply it to the finding of the longitude also; but for want of observations and experiments he could not make any progress. The affair was farther prosecuted by Mr Whiston, who published a treatise on the longitude, and for some time imagined it was possible to find it exactly by means of the dip of the needle; yet he at last despaired of it, for the following reasons: 1. The weakness of the magnetic power. 2. The concussion of the ship, which he found it exceeding difficult to avoid so much as was necessary for the accuracy of the experiments. 3. The principal objection was an irregularity in the motions of all magnetic needles, both horizontal and dipping, by which they, within the compass of about a degree, vary uncertainly backward and forward; even sometimes, in a few hours time, without any evident cause.
For a particular account of these variations both of the horizontal and dipping needle, see the article VARIATION.
Mr Nairne made a dipping-needle in 1772 for the board of longitude, which was used in the voyage towards the north-pole. This is represented Plate CCCXLV, fig. 2. The needle AA is 12 inches long, and its axis, the ends BB of which are made of gold alloyed with copper, rests on friction-wheels CCCC, of four inches diameter, each end on two friction-wheels; which wheels are balanced with great care. The ends of the axes of the friction-wheels are likewise of gold alloyed with copper, and moved in small holes made in bell-metal; and opposite to the ends of the axes of the needle and the friction-wheels, are flat agates, set in at DDD, finely polished. The magnetic needle vibrates within a circle of bell-metal, EEE, divided into degrees and half degrees; and a line, passing through the middle of the needle to the ends, points to the divisions. The needle of this instrument was balanced before it was made magnetic; but by means of a cross, the ends of which are FFFFF (contrived by the reverend Mr Mitchell) fixed on the axis of the needle, on the arms of which are cut very fine screws to receive small buttons, that may be screwed nearer or farther from the axis, the needle may be adjusted both ways to a great variety, after being made magnetic, by reversing the poles, and changing the sides of the needle. GG are two levels, by which the line of 0 degrees of the instrument is set horizontal, by means of the four adjusting screws LLLL; H is the perpendicular axis, by which the instrument may be turned, that the divided face of the circle may front the east or west; to this axis is fixed an index I, which points to an opposite line on the horizontal plate K when the instrument is turned half round; MMMM are screws which hold the glass cover to keep the needle from being disturbed by the wind. When this needle is constructed for sea, it is suspended by an universal joint on a triangular stand, and adjusted vertically by a plumb-line and button above the divided circle, and the dovetail work at the upper go; and the divisions on the circle are adjusted so as to be perpendicular to the horizon by the same plumb-line, and an adjoining screw; and when it is adjusted, a pointer annexed to a screw, which serves to move the divided circle, is fixed at the lowest go. Whenever the instrument is used to find the dip, it must be so placed that the needle may vibrate exactly in the magnetic meridian.
MAGNETICAL NEEDLES, in navigation, a needle touched with a lodestone, and sustained on a pivot or centre; on which playing at liberty, it directs itself to certain points in or under the horizon; whence the magnetic needle is of two kinds, viz. horizontal or inclinatory. See the article MAGNET.
Horizontal needles are those equally balanced on each side of the pivot that sustains them; and which, playing horizontally with their two extremes, point out the north and south points of the horizon. For their application and use, see the article COMPASS.
In the construction of the horizontal needle, a piece of pure steel is provided; of a length not exceeding six inches, lest its weight should impede its volubility; very thin, to take its verticity the better; and not pierced with any holes, or the like, for ornament sake, which prevent the equable diffusion of the magnetic virtue. A perforation is then made in the middle of its length, and a brass cap or head soldered on, whose inner cavity is conical, so as to play freely on a style or pivot headed with a fine steel point. The north point of the needle in our hemisphere is made a little lighter than the southern; the touch always destroying the balance, if well adjusted before; and rendering the north end heavier than the south, and thus occasioning the needle to dip.
The method of giving the needle its verticity or directive faculty has been shown already under the article MAGNET; but if, after touching, the needle be out of its equilibrium, something must be filed off from the heavier side, till it balance evenly.
Needles in sea compasses are usually made of a rhomboidal or oblong form: we have given their structure already under the article COMPASS.
The needle is not found to point precisely to the north, except in very few places; but deviates from it more or less in different places, and that too at different times; which deviation is called its declination or variation from the meridian. See the article VARIATION.
SURGEONS' NEEDLES are generally made crooked, and their points triangular; however they are of different forms and sizes, and bear different names, according to the purposes they are used for.
The largest are needles for amputation; the next, needles for wounds; the finest needles for sutures. They have others, very short and flat, for tendons; others, still shorter, and the eye placed in the middle, for tying together of vessels, &c. Needles for couching cataracts are of various kinds; all of which have a small, broad, and sharp point or tongue; and some with a fulcus at the point. Surgeons have sometimes used two needles in this operation; one with a sharp point for perforating the coats of the eye, and another with a more obtuse point for depressing or couching the opaque crystalline lens: but care should be taken in the use of any of these, that they be first well polished with cloth or leather, before they are applied to the eye.
Mr Warner observes, that the blade of the couching needle should be at least a third part larger than those generally used upon this occasion, as great advantages will be found in the depressing of the cataract, by the increased breadth of the blade of that instrument. The handle, also, if made somewhat shorter than usual, will enable the operator to perform with greater steadiness, than he can do with a larger handled instrument.
It is to be observed, that needles of silver pierce more easily in stitching arteries after an amputation, than those made of steel.
**Needle-Fish.** See *Sygnathus.*
**Needles,** sharp-pointed rocks north of the Isle of Wight. They are situated at the western extremity of the island, which is an acute point of high land, from which they have been disjoined by the washing of the sea. There were of these lofty white rocks formerly three, but about 14 years ago the tallest of them, called *Nefus's Wife,* which arose 120 feet above low-water mark, and in its shape resembling a needle, being undermined by the constant efforts of the waves, overleaped, and totally disappeared.
**Needs,** or St Neots, six miles from Huntingdon, 58 miles from London, so called from the monument of a saint of that name in it, who was burnt by the Danes, is a large well-built town, having a handsome strong church, with a prodigious fine steeple, and a good stone-bridge over the Ouse, by which coals are brought to it, and sold through the country. It has a charity-school for 25 poor children. Its market is on Thursday; fairs on Holy Thursday, Aug. 1, Corpus-Chrifti Thursday, June 13, and December 17; and it is famous for a medicinal spring.
**Needwood-Forest,** in Staffordshire, between the Trent, Dove, and Blythe, and near Uttoxeter, is said to exceed all the forests in England in the excellency of its soil and the fineness of its turf.
**NE EXEAT REGNO,** in law, is a writ to restrain a person from going out of the kingdom without the king’s licence. F. N. B. 85. It may be directed to the sheriff, to make the party find surety that he will not depart the realm, and on refusal to commit him to prison: or it may be directed to the party himself; and if he then goes, he may be fined. And this writ is granted on a suit being commenced against a man in the chancery, when the plaintiff fears the defendant will fly to some other country; and thereby avoid the justice and equity of the court; which hath been sometimes practised: and when thus granted, the party must give bonds to the matter of the rolls, in the penalty of 1000l. or some other large sum, for yielding obedience to it; or satisfy the court, by answer, affidavit, or otherwise, that he hath no design of leaving the kingdom, and give security.
**Nefer,** in Pembrokefhire, a village in whose church-yard is a remarkable old cross. The church has no pavement in it, and the frequent burials have raised the ground within it to seven or eight feet higher than without. In process of time, instead of a church, it will be only a sepulchre. It is pleasantly situated on the banks of a river of the same name near Newport.
**NEFASTI DIES** in Roman antiquity, an appellation given to those days wherein it was not allowed to administer justice, or hold courts. They were so called because, *non fari licet,* the praetor was not allowed to pronounce the three solemn words or formulas of the Negapatian law, *do, dico, addico,* I give, I appoint, I adjudge. These days were distinguished in the calendar by the letter N. for *nefastus*; or N. P. *Nefastus Primo,* when the day was only *nefastus* in the forenoon, or first part. The days of a mixed kind were called *intercisi.*
**NEGAPATAN,** a town of Asia in the peninsula on this side the Ganges, and on the coast of Coromandel. It was first a colony of the Portuguese, but was taken from them by the Dutch. The factory purchased very little besides tobacco and long linen cloths; however, the Dutch have thought proper to erect a fort here. It is situated in E. Long. 79° 10′ N. Lat. 11° 15′.
**NEGATION,** in logic, an act of the mind affirming one thing to be different from another; as that the foul is not matter. See Logic.
**NEGATIVE,** in general, something that implies a negation: thus we say, negative quantities, negative powers, negative signs, &c.
**NEGATIVE-Sign.** The use of the negative sign, in algebra, is attended with several consequences that at first sight are admitted with difficulty, and has sometimes given occasion to notions that seem to have no real foundation. This sign implies, that the real value of the quantity represented by the letter to which it is prefixed is to be subtracted; and it serves, with the positive sign, to keep in view what elements or parts enter into the composition of quantities, and in what manner, whether as increments or decrements, (that is, whether by addition or subtraction), which is of the greatest use in this art.
In consequence of this, it serves to express a quantity of an opposite quality to the positive, as a line in a contrary position; a motion with an opposite direction; or a centrifugal force in opposition to gravity; and thus often saves the trouble of distinguishing, and demonstrating separately, the various cases of proportions, and preserves their analogy in view. But as the proportions of lines depend on their magnitude only, without regard to their position, and motions and forces are said to be equal, or unequal, in any given ratio, without regard to their directions; and, in general, the proportion of quantity relates to their magnitude only, without determining whether they are to be considered as increments or decrements; so there is no ground to imagine any other proportion of — b and + a (or of — 1 and 1) than that of the real magnitudes of the quantities represented by b and a, whether these quantities are, in any particular case, to be added or subtracted. It is the same thing to subtract a decrement, as to add an equal increment, or to subtract — b from a — b, as to add + b to it: and because multiplying a quantity by a negative number implies only a repeated subtraction of it, the multiplying — b by — n, is subtracting — b as often as there are units in n; and is therefore equivalent to adding + b so many times, or the same as adding + n b. But if we infer from this, that 1 is to — n as — b to n b, according to the rule, that unit is to one of the factors as the other factor is to the product, there is no ground to imagine that there is any mystery in this, or any other meaning than that the real magnitudes represented by 1, n, b, and n b are proportional. For that rule relates only to the magnitude magnitude of the factors and product, without determining whether any factor, or the product, is to be added or subtracted. But this likewise must be determined in algebraic computations; and this is the proper use of the rules concerning the signs, without which the operation could not proceed. Because a quantity to be subtracted is never produced in composition by any repeated addition of a positive, or repeated subtraction of a negative, a negative square number is never produced by composition from the root. Hence $\sqrt{-1}$, or the square root of a negative, implies an imaginary quantity; and, in resolution, is a mark or character of the impossible cases of a problem, unless it is compensated by another imaginary symbol or supposition, when the whole expression may have a real signification. Thus $1 + \sqrt{-1}$, and $1 - \sqrt{-1}$ taken separately, are imaginary, but their sum is 2; as the conditions that separately would render the solution of a problem impossible, in some cases destroy each other's effect when conjoined. In the pursuit of general conclusions, and of simple forms representing them, expressions of this kind must sometimes arise where the imaginary symbol is compensated in a manner that is not always so obvious.
By proper substitutions, however, the expression may be transformed into another, wherein each particular term may have a real signification as well as the whole expression. The theorems that are sometimes briefly discovered by the use of this symbol, may be demonstrated without it by the inverse operation, or some other way; and though such symbols are of some use in the computations by the method of fluxions, its evidence cannot be said to depend upon arts of this kind. See Maclaurin's Fluxions, book ii. chap. 1. and Ludlam's Algebra, psalm.
NEGATIVE Electricity. See the article ELECTRICITY, psalm. See also POSITIVE Electricity.