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sebacic, the properties of which are quite as the rye ripens sooner than the wheat, distinct from those which had been for this method must be very exceptionable. merly described. The process by which The spring rye is sown along with oats, and Thenard obtained the sebacic acid is the usually ripens as soon as the winter rye; following. He distilled a qnantity of hogs- but the grain produced is lighter, and it is lard, and washed the product several times therefore seldom sown except where the with hot water. He then dropped into it autumnal crop has failed. Rye is comacetate of lead ; there was formed a flakey monly sown on poor, dry, limestone, or precipitate, which was collected and dried, sandy soils, where wheat will not thrive. By put into a retort with sulphuric acid, and continuing to sow it on such a soil for two heated. The liquor in the receiver bad no or three years, it will at length ripen a acid character ; but there appeared in the month earlier than that which has been retort a melted matter analogous to fat. raised for years on strong cold ground. This is carefully separated; and after being SECANT, in geometry, is a line that washed, is boiled with water. By the cuts another, or divides it into two parts. action of heat the whole is dissolved by the In trigonometry, the secant denotes a water, and when it cools, crystals in the right line drawn from the centre of a circle, shape of needles are deposited. These are which cutting the circumference, proceeds the sebacic acid which has the following till it meets with a tangent to the same circle. properties. It has no smell, a slight acid SECHIUM, in botany, a genus of the taste, and reddens strongly the tincture of Monoecia Syngenesia class and order. Naturnsole. When heated it melts like tallow. tural order of Euphorbiæ, Jussieu. Essential It is much more soluble in warm than 'in character : calyx half, five-cleft; corolla cold water. Alcohol dissolves it in large five-cleft, with ten bollows in the upper quantities. Boiling water saturated with part of the tube ; nectary : male, filaments this acid forms a solid mass on cooling. It five, connected : female, stigma very large, crystallizes in small needles, but with certain peltate reflexed, five-cleft ; pericarpium precautions may be obtained in the form of large, ovate, turbinate, one-seeded. There long, large, and very brilliant plates. It pre- is only one species, viz. S. edule, the chocho cipitates the acetate and nitrate of mercury vipe. It is a native of the West Indies ; and lead, and nitrate of silver; it neutralizes flowering and fruiting in December. the alkalies, and forms with them soluble SECOND, in geoinetry, chronology, &c. salts.

the sixtieth part of a prime or minute ; SEBATES, in chemistry, salts formed of whether of a degree, or of an hour ; it is the sebacic acids, and alkalies, earths, &c.; denoted by two small accents, thus (0 ). they are soluble in water.

SECRETARY, an officer who by his SECALE, in botany, rye, a genus of the master's orders writes letters, dispatches, Triandria Digynia class and order. Natu. and other instruments, which he renders ral order of Gramina or Grasses. Essential authentic by his signet. Of these there are character: calyx opposite, two-valved, several kinds ; as, 1. Secretaries of State, two-flowered, solitary. There are four who are officers that have under their ma. species, viz, the villosum, orientale, creti. nagement and direction the most important cum, and cercale. S. villosum, or wood rye. affairs of the kingdom, and are obliged grass, is distinguished by a calyx with constantly to attend on the King: they rewedge-shaped scales, and by the fringe of ceive and dispatch whatever comes to their the glume being woolly. The glumes of the hands, either from the crown, the church, S, orientale are shaggy, and the scales of the the army, private grants, pardons, dispen calyx are shaped like an awl. The glumes sations, &c. as likewise petitions to the soof the S. creticam are fringed on the outside. vereign, wbich, when read, are returned to The S. cereale, or common rye, has glumes them; all which they dispatch according to with rough fringes. It is a native of the the King's direction. They have authority to island of Candia, was introduced into Eng. commit persons for treason and other of. land many ages ago, and is the only species fences against the state, as conservators of of rye cultivated in this kingdom. There the peace, at common law, or as justices are, however, two varieties, the winter and of the peace throughout the kingdom. They spring rye. The winter rye, which is are members of the Privy Council, which larger in the grain than the spring rye, is is seldom or never held without one of them sown in autumn at the same time with being present; and as to the business and wheat, and sometimes mixed with it ; b correspondence in all parts of this kingdom, it is managed by either of the secretaries, &c. adapted to any radius between the length without any distinction ; but with respect and breadth of the sector, when opened. to foreign affairs the business is divided into The sector is founded on the fourth propotwo provinces or departments, the southern sition of the sixth book of Euclid, where it and the northern, comprehending all the is demonstrated, that similar triangles bave kingdoms and states that have any inter their homologous sides proportional. See course with Great Britain ; each secretary MATHEMATICAL INSTRUMENTS. receiving all letters and addresses from, and SECUNDINES, after birth, in anatomy, making all dispatches to, the several princes the several coats or membranes wherein and states comprehended in his province. the fætus is wrapped up in the mother's 2. Secretary of an Embassy, a person at- womb, as the chosion and amnios, with the tending an embassador for writing dispatches placenta, &c. See MIDWIFERY. relating to the negociation. There is a great S ECURIDACA, in botany, a genus of difference between the secretary of an em. the Diadelphia Octandria class and order. bassy, and the embassador's secretary; the Natural order of Papilionaceæ, or Legumilast being a domestic or menial of the em nosæ. Essential character: calyx threebassador, and the first a servant or minister leaved; corolla papilionaceous, with the of the prince. 3. The Secretary of War, standard two-leaved within the wings; le. an officer of the War Office, who has two gume ovate, one-celled, one-seeded, ending chief clerks under him, the last of which is in a ligulate wing. There are three spethe secretary's messenger. There are also cies. secretaries in most of the other offices. SEDUM, in botany, stonecrop, a genus

SECRETION, In the course of the of the Decandria Pentagypia class and circulation the blood is conveyed to certain order. Natural order of Succulentæ. Semorgans named glands, and is there entirely pervivæ, Jussieu. Essential character: ca. changed in its chemical composition, so as lyx five-cleft; corolla tive-petalled ; scales to form various products not pre-existing in nectariferous, five, at the base of the germ ; the mass of blood, and which form some of capsules five. There are thirty species, all the most important varieties of aniinal mat, of which are hardy, herbaceous, succulent ter. See PHYSIOLOGY.

perennials, durable in root, but mostly anSECTION, in geometry, denotes a side nual in stalk, &c. which, rising in spring, or su face appearing of a body or figure cut flower in June, July, and August, in dif: by another; or the place where lines, planes, ferent sorts ; the Powers consisting univer. &c. cut each other. The common section sally of five spreading petals, generally ot' two planes is always a right line; being crowning the stalks numeronsly in corymthe line supposed to be drawn on one bose and cymose bunches and spikes, ap. plane by the section of the other, or by its pearing tolerably conspicuous, and are sucentrance into it.

ceeded by plenty of seeds iu autumn, by SECTION of a building, in architecture, which they may be propagated, also abunis the same with its profile ; or a delinea. dantly by parting the roots, and by slips tion of its heights and depths raised on a or cuttings of the stalks in summer; in all plane, as if the fabric was cut asunder to of which methods they readily grow, and discover its inside.

spread very fast into tufted bunches : being SECTOR, in geometry, is a part of a all of succulent growth, they consequently circle, comprehended between two radii delight most in dry soils, or in any dry ruband the arch; or it is a mixed triangle, bishy earth. As flowering plants, they are formed by two radii and the arch of a mostly employed to embellish rock-work, circle.

ruins, and the like places; planting either Sector is also a mathematical instru the roots or cuttings of the shoots in a little ment, of great use in tinding the proportion mud or any moist soil at tirst, placing it in between quantities of the same kind, as be the crevices, where they will soon root and tween lines and lines, surfaces and surfaces, fix themselves, and spread about very agree. &c. for which reason the French call it the ably. compass of proportion.

SEED, in botany, the esseoce of the The great advantage of the sector above fruit of every vegetable. Linnæus deno. common scales, &c. is, that it is adapted to "minates it to be a deciduous part of the all radii, and all scales. For, by the line of plant, containing the rudiments of the new chords, sines, tangents, &c. on the sector, vegetable, and fertilized by the sprinkling we have lines of chords, sines, tangents, of the male dust, Plants are furnished with

one seed as the sea-pink; or two as in um- base, add the square of its height: multiply bellefcrous plants; or three as in the spurge: the sum by the height, and the product by or many as in the ranunculus, &c. The .5236. Or, 2dly, From three times the shape, structure, and sides of sceds are va- diameter of the sphere, subtract twice the rious. Linnæus denominates seeds the height of the frustrum; multiply the remain. eggs of plants; and tre fecundity of plants der by the square of the height, and the prois often astonishing: there are 4,000 seeds duct by .5236. in a single sun-flower; more than 30,000 SEGUIERIA, in botany, so named in in a poppy; and in a single tobacco plant honour of Jean François Seguier, a cenns 360,000 have been enumerated. The an. of the Polyandria Monogynia class and nual produce of a single stalk of spleen. order. Essential character: calyx, fiveworth has been estimated to be a million leaved; corolla none; capsule, one-seeded, of seeds. Plants are disseminated in va- terminated by a large wing, baving small rious methods : some are carried along by lateral ones. There are two species, riz. rivers and torrents many hundred miles S. Americana and S. Asiatica. from their native soil, and cast upon a very SEISIN, is two-fold, seisin in law, and different climate, to which, however, by de- seisin in fact. Seisin in fact, is when an grees they render themselves familar. Some actual possession is taken; seisin in law. åre formed by wings to be borne before when something is done, which the law acthe wind to distant places. Birds, squir- counts a seisin. See Estate, Fee, &c. rels, &c. swallow seeds, and void them S ELAGO, in botany, a genus of the Didywhole and fit for vegetation, and thus dis- Damia Gymnospermia class and order. Naseminate them. There are others that dis- tural order of Aggregatæ. Vitices, Jussieu. perse themselves by an elastic force, that Essential character : calyx, five-cleft; coresides either in the “ calyx”, as in oats and rolla, tube capillary, border almost equal; the ferns: in their “pappus", as in the seed one or two. There are twenty species. " centaurea cropina”, or in their capsule, as These plants are herbaceous or shrubby; in the geranium.

all natives of the Cape of Good Hope. Seed. See SEMEN.

· Leaves alternate; flowers in most of the SEGMENT of a circle, in geometry, that species, allied to those of eranthemum and part of the circle contained between a verbena, irregular, tubular, in alternate chord and an arch of the same circle. - terminating spikes, which are simple or

SEGMENT of u sphere, is a part of a sphere manifold; in a few, the flowers are regular, terminated by a portion of its surface, and with a short two seeded tube, in a sort of a plane which cuts it off, passing somewhere terminating corymb. , out of the centre; being more properly SELENITE, in mineralogy, a species called the section of a sphere. The base of the Calc genus, is of a snow white colour, of such a segment, it is evident, is always a passing into different shades of grey. It circle. And the convex surfaces of different is most generally massive, and not unfre. segments, are to each other as their alti. qnently crystallized; the crystals are seltudes, or versed sines. And as the whole dom large; internally, its lustre shining and convex surface of the sphere is equal to splendent. The fracture is perfectly foliat. four of its great circles, or four circles of ed. It is transparent, soft, and not parthe same diameter; so the surface of any ticularly frangible ; specific gravity 2.3; it segment is equal to four circles on a dia- is composed of lime, sulphuric acid, and meter equal to the chord of half the arc of water, and is found in Germany, France. the segment. So that if d denotes the dia. and England. On account of its great mieter of the sphere, or the chord of half purity it is employed in taking the most the circnmference, and c the chord of half delicate impressions ; it is also used for the arc of any other segment, also a the crayons, and when burnt and powdered. altitude or versed sine of the same; then, it is used for cleansing silver. It is the same 3.1416" is the surface of the whole

with GYPSUM, under which word will be

e found some other particulars relating to it. sphere, and

SELEUCIDE, in chronology. Era of 3.14106, or 3.1416d, the surface of the

the Seleucidæ, or the Syro Macedonian æra,

is a computation of time, commencing from For the solid content of a segment, there the establishment of the Seleucidæ, a race are two rules usually given; riz. 1. To of Greek kings, who reigned as successors three times the square of the radius of its of Alexander the Great, in Syria, as the

segment.

Ptolemies did in Egypt. This æra we find transparent crystals of a line in length, expressed in the book of the Maccabees, crossing each other like radii from a centre. and on a great number of Greek medals, When they are magnified, they appear to struck by the cities of Syria, &c. The rab- be four-sided prisms terminated by long bins call it the æra of contracts; and the four-sided pyramids. When semen is exArabs therik dilkarnain, that is, the æra of posed to a warm air, in considerable quan. the two horns. According to the best ac- tity, it is decomposed; it assumes the colour counts, the first year of this æra falls in the of the yolk of egg, and becomes acid, either year 311 before Christ, being twelve years by absorbing the oxygen from the atmos. after Alexander's death,

phere, or by a different combination and SELINUM, in botany, a genus of the arrangement of its own constituent prinPentandria Digynia class and order. Na- ciples. Heat accelerates the liquefaction tural order of Umbellatæ or Umbelliferæ. of semen; and when it has undergone this Essential character: petals, cordate, eqnal; change it is no longer susceptible of coaguinvolucre, reflex; fruit oval, oblong, como lation. It is decomposed by the applicapressed, flat, striated in the middle. There tion of strong heat. Water is first sepa. are nine species.

rated; it then blackens, swells up, and SELL, in building, is of two kinds, viz. emits yellow fumes, having an empyrenground-sell, which denotes the lowest piece matic, ammoniacal odour. A light coal reof tiniber in a timber building, and that on mains behind, which burns readily to white which the whole superstructure is raised; ashes. and the window-sell, is the bottom piece The acids readily dissolve semen, and in a window-frame.

this solution is not decomposed by the al. SEMECARPUS, in botany, a genus of kalies ; nor indeed is the alkaline solution the Pentandria Trigynia class and order. of semen decomposed by the acids. Wine, Essential character: calyx inferior, five cider, and urine, also dissolve semen, but cleft; corolla, five petalled; nut, kidney. it is in consequence of the acid which is form, inserted into a large fleshy, flattened combined with these liquids. The crystals receptacle. There is but one species, riz. which form in semen by spontaneous evaS. anacardium, marking nut tree. It is a poration in the open air, and which are en. native of all the mountainous parts of India, tangled in the viscid matter, may be sepaflowering in July and August.

rated by adding water. SEMEN. See PhysioLOGY. Semen These crystals have neither smell por is secreted in the testes of male animals; taste. They melt under the blow-pipe into but when it is ejected it is composed of a white opaque globnle, which is surrounded two substances; the one is fluid and milky, with a yellowish flame. This salt is insolu. and the other of a thick mucilaginous con- ble in water, and is not acted on by the sistence, in which appear a great number alkalies; but is soluble in the mineral acids of white silky filaments, especially if it without effervescence, from which solutions, be agitated in cold water. It has a dis- lime water, the alkalies, and oxalic acid agreeable odour, and an acrid irritating throw down a precipitate. The component taste. The specific gravity varies consider parts of semen are found to be ably, but is always greater than that of water. When it is rubbed in a mortar, it

........................... 90 froths up, and acquires the consistence of

Mucilage pomatum from the air with which it mixes.

Soda............................. It converts the flowers of violets, to a green

Phosphate of lime............_ colour, and it precipitates the calcareous and metallic salts, which shows, that it contains an uncombined alkali. The thick SEMICIRCLE, in geometry, balf a cir. part of the semen as it cools, becomes cle, or that tigure comprehended between transparent, and assumes a greater degree the diameter of a circle and half the circum. of consistence; but it afterwards becomes ference. entirely liquid, even without absorbing, SEMICOLON, in grammar, one of the moisture from air. If semen be exposed points or stops used to distinguish the seveto the air after it has become liquid at the ral members of sentences from each other. temperature of sixty degrees, it becomes See PUNCTUATION. covered with a transparent pellicle, and at SEMICUBICAL parabola, in the higher the end of three or four days deposits fine geometry, a curve of the second order,

Water

100

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wherein the cubes of the ordinates are as bolas, y" : ""::aa"--:9:"-1=2-1: the squares of the abscisses. Its equation 29-'; or the powers of the semiordinates is axx = y.

are, as the powers of the semiabscisses The area of the space A PM (Plate XIV. one degree lower; for instance, in cubical Miscel, fig. 1), is = 4 xy = APX semiparabolas the cubes of the ordinates PM, or 1 of the circumscribing rectangle. are as the squares of the abscisses; that is, The content of the solid generated by the y? : 0}::x : z. revolation of the space APM about the SEMPERVIVUM, in botany, houseleek, axis A P, is 4 prys = .7854 APX PM?, or a genus of the Dodecandria Polygynia class

of the circumscribing cylinder. And a and order. Natural order of Succulentæ. circle equal to the surface of that solid may Sempervivæ, Jussien. Essential character: be found from the quadrature of an liyper. calyx twelve-parted; petals twelve ; cap. bolic space. Also the length of any arc, sule twelve, many-seeded. There are fourAM, of the curve may be easily obtained teen species. from the quadrature of a space contained SENECIO, in botany, groundsel, a ge. under part of the carve of the common nus of the Syogenesia Polygamia Superparabola, two semi-ordinates to the axis, and fua class and order. Natural order of the part of the axis contained between Compositæ Discoideæ, Corymbiferæ, Justhem. This curve may be described by a sieu. Essential character: calyx cylindricontinued motion, viz. by fastening the cal, calycled, with the scales mortified at angle of a square in the vertex of a com- the tip; down simple; receptacle naked. mon parabola ; and then carrying the inter. There are seventy-five species. section of one side of this square and a long S ENSATION. The brain is a soft pulpy ruler (which ruler always moves perpen- mass, of a whitish colour on the inside, ocdicular to the axis of the parabola) along cupying all the cavity of the skull. Minute the curve of that parabola. For the inter- differences are observable in the substance section of the ruler, and the other side of of the brain in different parts of it, but it is the square will describe a semicubical para unnecessary to enter upon a statement of bola. Maclaurin performs this without a them here. (See ANATOMY.) The spinal common parabola, in his Geometria Or. marrow is the continuation of the lowest ganica.

part of the brain, which passes through the SEMIDIAMETER, half the diameter, or great opening of the skull down the hollow a right line drawn from the centre of a cir- of the back bone. The substance concle, or sphere, to its circumference; being tained in the hollow of the back bone is the same with what is otherwise called the the same with that in the cavities of the radius. The distances, diameters, &c. of skull; and it is sometimes convenient to the heavenly bodies, are nsually estimated, comprehend both the portions under the by astronomers, in semidiameters of the same general name of brain. From the . earth; and the distances of the secondary brain proceeds the nerves, which at first planets from their respective primary ones, are fine fibres of the same substance with by semidiameters of the body of the pri. the brain : these fibres meet and form soft mary planet.

white polpy cords, which afterwards spread Suppose the semidiameter of the Earth themselves over various parts of the body, to be unity, then the measures of the Sun by splitting into innumerable and exceed. and planets will be as follow: The semi- ingly minute branches. Anatomists count diameter of

forty pairs of nerves, (for they come off in The Earth........................ 1 pairs, though they afterwards separate), and The Sun ......................... 111.25 of those nine or ten only come from the The Moon ................... 0.27

brain at the bottom of the skull, and the Mercury ........................ 0.38 rest from the spinal marrow. Those from Venus

1.15 the brain are distributed to various parts M ars .............................. 0.65

of the head"; those from the spinal marrow Jupiter ............................ 11.81

are distributed over the trunk and extremiSaturn ..................

ties. The external organs of sense, the Herschel

4.32 nerves, and the brain, are the organs of

sensation. All, as we are at present constiSEMIPAKABOLA, in geometry, a curve tuted, are necessary to sensation. If the defined by the equation ax" -' =y" ; external organ is destroyed no sensation as a m = y', and a r = y*. Io semipara. can be produced : where there are no nerves

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