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Philosophical Transactions for the years The winter rye, which is largerin the graini 1780 and 1782 But it appears, that the than the spring rye, is sown in autumn, acid obtained by those who first treated at the same time with wheat, and someof the subject was either the acetic acid, times mixed with it; but as the rye ripens or some acid different from the sebacic, sooner than the wheat, this method must the properties of which are quite distinct be very exceptionable. The spring rye from those which had been formerly de. is sown along with oats, and usually riscribed. The process by which Thenard pens as soon as the winter rye ; but the obtained the sebacic acid is the following. grain produced is lighter, and it is thereHe distilled a quantity of hog's lard, and fore seldom sown except where the auwashed the product several times with tumnal crop has failed. Rye is commonhot water. He then dropped into it ace- ly sown on poor, dry, limestone, or sandy tate of lead ; there was formed a Aaky soils, where wheat will not thrive. By precipitate, which was collected and continuing to sow it on such a soil for two dried put into a retort with sulphuric or three years, it will at length ripen a acid and heated. The liquor in the re- month earlier than that which has been ceiver had no acid character; but there raised for years on strong cold ground. appeared in the retort a melted matter SECANT, in geometry, is a line that analogous to fat This is carefully sepa. cuts another, or divides it into two parts. rated, and after being washed, is boiled I n trigonometry, the secant denotes a with water. By the action of heat the right line drawn from the centre of a cirwhole is dissolved by the water, and cle, which, cutting the circumference,pro. when it cools, crystals in the shape of ceeds till it meets with a tangent to the needles are deposited. These are the same circle. sebacic acid, which has the following pro. SECHIUM, in botany, a genus of the perties. It has no smell, a slight acid Monoecia Syngenesia class and order. taste, and reddens strongly the tincture of Natural order of Euphorbiæ, Jussieu. Es. turnsole. When heated it melts like tal. sential character: calyx half five-cleft; low. It is much more soluble in warm corolla five-cleft, with ten bollows in the than in cold water. Alcohol dissolves it upper part of the tube ; nectary; male, in large quantities. Boiling water satu- filaments five, connected ; female, stigma rated with this acid forms a solid mass on very large, peltate reflexed, five-cleft ; cooling. It crystallizes in small needles, pericarpium large, ovate, turbinate, onebut with certain precautions may be ob. seeded. There is only one species, viz. tained in the form of long, large, and S. edule, the chocho vine It is a native very brilliant plates. It precipitates the of the West Indies ; flowering and fruitacetate and nitrate of mercury and lead, ing in December. and nitrate of silver; it neutralizes the al. SECOND, in geometry, chronology, kalies, and forms with them soluble salts. &c. the sixtieth part of a prime or mi.

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

SECALE, in botany, rye, a genus of the SECRETARY, an officer, who by his Triandria Digynia class and order. Natu- master's orders writes letters, despatches, ral order of Gramina or Grasses Essen- and other instruments, which he renders tial character: calyx opposite, two-valved, authentic by his signet. Of these there two-flowered, solitary. There are four spe. are several kinds; as, 1. .Secretaries of cies, viz. the villosum, orientale,creticum, State, who are officers that have under and cereale. S villosum, or wood-rye. their management and direction the most grass, is distinguished by a calyx with important affairs of the kingdom, and are wedge-shaped scales, and by the fringe of obliged constantly to attend on the King; the glume ieing woolly. The glumes of they receive and dispatch whatever comes the s. orientale are shaggy, and the to their hands, either from the crown scales of the calyx are shaped like an awl. the church, the army, private grants, parThe glumes of the S creticum are fringed dons, dispensations, &c. as likewise peon the outside. The S.cereale, or common titions to the sovereign, which, when sye, has glumes with rough fringes. It is read, are returned to them ; all which a native of the island of Candia, was they dispatch according to the King's diintroduced into England many ages ago, rection. They have authority to commit and is the only species of rye cultivated persons for treason, and other offences in this kingdom. There are, however, against the state, as conservators of the two varieties, the winter and spring rye, peace at common law, or as justices of VOL. XI.





the peace throughout the kingdom. The great advantage of the sector above
They are members of the Privy Council, common scales, &c. is, that it is adapted
which is seldom or never held without to all radii, and all scales. For, by the
one of them being present; and as to the line of chords, sines, tangents, &c. on the
business and correspondence in all parts sector, we have lines of chords, sines, tan-
of this kingdom, it is managed by either gents, &c. adapted to any radius between
of the secretaries, without any distinc. the length and breadth of the sector,
tion ; but, with respect to foreign affairs, when opened. The sector is founded on
the business is divided into two provin. the fourth proposition of the sixth book of
ces or departments, the southern and the Euclid, where it is demonstrated, that
northern, comprehending all the king- similar triangles have their homologous
doms and states that have any intercourse sides proportional. See MATUEMATICAL
with Great Britain ; each secretary receiv. INSTRUMENTS.
ing all letters and addresses from, and SECUNDINES, after birth, in anatomy,
making all dispatches to, the several the several coats or membranes wherein
princes and states comprehended in his the fætus is wrapped up in the mother's
province. 2. Secretary of an Embassy, a womb, as the chorion and amnios, with
person attending an ambassador for writ. the placenta, &c. See MIDWIFERY.
ing dispatches relating to the negotiation. SECURIDACA, in botany, a genus of
There is a great difference between the the Diadelphia Octandria class and order.
secretary of an embassy, and the ambas. Natural order of Papilionacex, or Legu-
sador's secretary; the last being a domes. minosæ. Essential character: calyx three-
tic or menial of the ambassador, and the leaved ; corolla papilionaceous, with the
first a servant or minister of the prince. standard two-leaved within the wings;
3. The Secretary of War, an officer of legume ovate, one-celled, one-seeded,
the War Office, who has two chief clerks ending in a ligulate wing. There are three
under him, the last of which is the secre. species.
tary's messenger. There are also secre. SEDUM, in botany, stonecrop, a genus
taries in most of the other offices. of the Decandria Pentagynia class and

SECRETION. In the course of the order. Natural order of Succulentæ. circulation the blood is conveyed to cer. Sempervivæ, Jussieu. Essential charactain organs named glands, and is there ter: calyx five.cleft; corolla five-petalled ; entirely changed in its chemical composi. scales nectariferous, five, at the base of tion, so as to form various products not the germ ; capsules five. There are pre-existing in the mass of blood, and thirty species, all of which are hardy, which form some of the most important herabceous, succulent perennials, duravarieties of animal matter. See Physio. ble in root, but mostly annual in stalk, &c. LOGY.

which, rising in spring, flower in June, SECTION, in geometry, denotes a side July and August, in different sorts; the or surface appearing of a body or higure Aowers consisting universally of five cut by another; or the place where lines, spreading petals, generally crowning the planes, &c. cut each other. The common stalks numerously in corymbose and cysection of two planes is always a right mose bunches and spikes, appearing tole. line; being the line supposed to be rably conspicuous, and are succeeded by drawn on one plane by the section of the plenty of seeds in autumn, by which they other, or by its entrance into it.

may be propagated; also abundantly by Section of a building, in architecture, parting the roots, and by slips or cuttings is the same with its profile ; or a delinea. of the stalks in summer: in all of which tion of its heights and depths raised on a methods they readily grow, and spread plane, as if the fabric was cut asunder to very fast into tufted bunches: being all discover its inside.

of succulent growth, they consequently SECTOR, in geometry, is a part of a delighit most in dry soils, or in any dry circle comprehended between iwo radii rubbishy earth. As flowering plants, and the arch; or it is a mixed triangle, they are mostly employed to embellish formed by two radii and the arch of a, ruins, and the like places ; circle.

planting either the roots or cuttings of Sector is also a mathematical instrument, the shoots in a little mud or any moist of great use in finding the proportion be. soil, at first placing it in the crevices, tween quantities of the same kind, as be. where they will soon root and fix themtween lines and lines, surfaces and surfa. selves, and spread about very agreeably. ces, &c. for which reason the French call SEED, in botany, the essence of the it the compass of proportion.

fruit of every vegetable, Linnæus deno.

minates it to be a deciduous part of the For the solid content of a segment plant, containing the rudiments of the there are two rules usually given; viz. 1. new vegetable, and fertilized by the Tothree times the square of the radius of sprinkling of the male dust. Plants are its base, add the square of its height; furnished with one seed, as the sea-pink; multiply the sum by the height, and the or two, as in limbelliferous plants; or product by 5236. Or, 2dly, From three three, as in the spurge; or many, as in times the diameter of the sphere, subtract the ranunculus, &c. The shape, structure, twice the height of the frustrum; multiand sides of seeds are various. Linnæus ply the remainder by the square of the denominates seeds the eggs of plants; height, and the product by .5236. and the fecundity of plants is often asto. SEGUIERIA, in botany, so narned in nishing: there are 4.000 seeds in a single honour of Jean Francois Seguier, a genus sun-flower: more than 30,000 in a poppy:

of the Polyandria Monogynia class and and in a single tobacco plant 360,000 have order. Essential character: calyx, fivebeen enumerated. The annual produce leaved; corolla none; capsule, one-seed. of a single stalk of spleenwort has been ed, terminated by a large wing, having estimated to be a million of seeds. Plants small lateral ones. There are two species, are disseminated in various methods : viz. S. Americana and S. Asiatica. some are carried along by rivers and tor- SEISIN, is two-fold, seisin in law, and rents many hundred miles from their na. seisin in fact. Seisin in fact, is when an tive soil, and cast upon a very different actual possession is taken: seisin in law, climate, to which, however, by degrees, wlien something is done, which the law they render themselves familiar. Some accounts a seisin. See ESTATE, FEE, &c. are formed by wings, to be borne before

SELAGO, in botany, a genus of the the wind to distant places Birds, squir Didynamia Gymnospermia class and or. rels, &c. swallow seeds, and void them der. Natural order of Aggregatæ. Viti. whole and fit for vegetation, and thus dis ces, Jussieu. Essential character: calyx, seminate them. There are others that five-cleft; corolla, tube capillary, border disperse themselves by an elastic force, almost equal; seed one or two. There that resides either in the “calyx," as in are twenty species. These plants are oats and the ferns: in their “ pappus,” herbaceous or shrubby: all natives of the as in the "centaurea crupina,” or in their Cape of Good Hope. Leaves alternate ; capsule, as in the geranium.

Howers in most of the species allied to SEED. See SEMEN.

those of eranthemum and verbena, irreSEGMENT of a circle, in geometry, gular, tubular, in alternate terminating that part of the circle contained between spikes, which are simple or manifold; in a chord and an arch of the same circle. a few, the fowers are regular, with a

SEGMENT of u sphere, is a part of a short two seeded tube, in a sort of termi. sphere terminated by a portion of its sur. nating corymb face, and a plane which cuts it off, pass. SELENITE, in mineralogy, a species ing somewhere out of the centre; being of the calc genus, is of a snow white comore properly called the section of a lour, passing into differen shades of grey. sphere. The base of such a segment, it is it is most generally massive, and not unevident, is always a circle. And the con. freq'iently crystallized; the crystals are vex surfaces of different segments are to seldom large; internally, its lustre shin. each other as their altitudes or versed ing and splendent. The fracture is persines. And as the whole convex surface fectly foliated. It is transparent, soft, and of the sphere is equal to four of its great not particularly frangible; specific gravity, circles, or four circles of the same diame. 2.3 : it is composed of lime, sulphuric ter; so the surface of any segment is acid, and water; and is found in Germany, equal to four circles on a diameter equal France, and England. On account of its to the chord of half the arc of the segment. great purity it is employed in taking the So that if d denotes the diameter of the most delicate impressions: it is also used sphere, or the chord of half the circum- for crayons, and when burnt and powder. ference, and c the chord of half the arc of ed, it is used for cleansing silver. It is the any other segment, also a the altitude or same with GYPSUM, under which word versed sine of the same; then,

will be found some other particulars re. 3.1416dis the surface of the whole lating to it. sphere, and

SELEUCIDÆ, in chronology. Æra of 3.1416co, or 3.1416d the surface of the the Seleuciilæ, or the Syro-Macedonian segment.

ära, is a computation of time, commencing

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from the establishment of the Seleucidæ, degrees, it becomes covered with a trans. a race of Greek kings, who reigned, as parent pellicle, and at the end of three or successors of Alexander the Great, in Sv. four days deposits fine transparent crysria, as the Ptolemies di! in Egypt. This tals of a line in length, crossing each æra we find expressed in the book of the other like radii from a centre. When Maccabees, and on a great number of they are magnified, they appear to be Greek medals, struck by the cities of Sy four-sided prisms, terminated by long ria, &c. The rabbins call it the æra of four-sided pyramids. When semen is excontracts; and the Arabs therik dilkar posed to a warm air, in considerable quan. nain, that is, the æra of the two horns. tity, it is decoinposed; it assumes the According to the best accounts, the first colour of the volk of egg, and becomes year of this æra falls in the year 311 be- acid, either by absorbing the oxygen from fore Christ, being twelve years after Alex. the atmosphere, or by a different combiander's death,

nation and arrangement of its own constiSELINUM, in botany, a genus of the tuent principles. Heat accelerates the Pentandria Digynia class and order. Na- liquefaction of semen; and when it has tural order of Umbellatæ or Umbelliferæ. undergone this change, it is no longer Essential character: petals cordate, susceptible of coagulation. It is decom. equal; involucre, reflex; fruit oval, ob posed by the application of strong heat. long, compresseil, fat, striated in the Water is first separated; it then blackens, middle. There are nine species.

swells up, and emits vellow fumes, having SELL, in building, is of two kinds, viz. an empyreumatic, ammoniacal colour. A ground-sell, which denotes the lowest light coal remains behind, which burns piece of limber in a timber building, and readily to white ashes. that on which the whole superstructure is The acids readily dissolve semen, and raised; and the window.sell is the bottom this solution is not decomposed by the piece in a window-frame.

alkalies; nor indeed is the alkaline soluSEMECARPUS, in botanv, a genus o tion of semen decomposed by the acids. the Pentandria Trigynia class and order. Wine, cider, and urine, also dissolve seEssential character: calyx, inferior, five. men, but it is in consequence of the acid cleft ; corolla, five-petalled ; nut, kidney. which is combined with these liquids. form, inserted into a large, fesby, Aatten. The crystals which form in semen by ed receptacle. There is but one species, spontaneous evaporation in the open air, riz. S. anacarilium, marking nut tree. It and which are entangled in the viscid is a native of all the mountainous parts of matter, may be separated by adding India, flowering in July and Auglist. Water.

SEMEN. See PHYSIOLOGI Semen is These crystals have neither smell nor secreted in the testes of male animals; taste They melt under the blow-pipe but when it is ejected it is composed of into a white opaque globule, which is two substances; the one is fuid and surrounded with a yellowish tlame This milky, and the other of a thick mucilagi salt is insoli:ble in water, and is not acted nous consistence, in which appear a great on by the alkalies; but is soluble in the number of white, silky filaments, especi. mineral acids without effervescence, from ally if it be agitated in cold water li has which solutions lime water, the alkalies, a disagreeable odour, and an acrid irritat. and oxalic acid, throw down a precipitate. ing taste. The specific gravity varies con. The component parts of semen are found sislerably, but is always greater than that to be of water when it is rubberl in a mortar, it froths up, and acquires the consistence

Water . . . . . . 90 of pomatum from the air with which it

Mucilage · · · · mixes It converts the powers of violets

Soda . . . . . . 1 to a green colour, and it precipitates the

Phosphate of lime .. 3 calcareous and metallic salts, which shows that it contains an incombined alkali.

100 The thick part of the semen, as it cools, becomes transparent, and assumes 'a greater degree of consistence; but it af. terwards becomes entirely liquid, even SEMICIRCLE, in geometry, half a cirwithout absorbing moisture from air if cle, or that figure comprehended be. scmen be exposed to the air after it has tween the diameter of a circle and half become liquid at the temperature of sixty the circumference.

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SEMICOLON, in grammar, one of the SEMIPARABOLA, in geometry, a points or stops used to distinguish the curve defined by the equation armois several members of sentences from each ym; as a r = y, and a ri = yt. In semiother. See Punctuation.

parabolas, ym : um ; : a.xm-:azm- = SEMICUBICAL parabola, in the higher in- :m-, or the powers of the semigeometry, a curve of the second order, ordinates are as the powers of the semiwherein the cubes of the ordinates are alsscisses one degree lower; for instance, as the squares of the abscisses. Its equa. in cubical semiparabolas the cubes of the tion is arr = y3.

ordinates are as the squares of the ab. The area of the space APM (Plate scisses; that is, y' : v} :: r.::. XIV. Miscel. fig. 1.) is = try =

SEMPERVIVOM in botany, houseleek, AP XPM, or 4. of the circumscribing a genus of the Dodecandria Polygynia

class and order. Natural order of Succurectangle. The content of the solid ge. nerated by the revolution of the space

lentæ Sempervivæ, Jussieu. Essential APM about the axis A P, is + px y

character: calyx twelve-parted; petals

= twelve ; capsule twelve, many-seeded, .7854 AP X P M’, or of the circumscribing cylinder.

There are fourteen species. And a circle equal to the surface of that solid may be found

SENECIO, in botany, groundsel, a gefrom the quadrature of an hyperbolic

nus of the Syngenesia Polygamia Superspace. Also the length of any arc AM, flua class and order. Natural order of of the curve may be easily obtained from Compositæ Discoideæ. Corymbiteræ. the quadrature of a space contained

ontained Jussieu. Essential character: calyx cyunder part of the curve of the common Tindrical, calycled, with the scales mortiparabola, two semi-ordinates to the axis fied at the tip; down simple : receptacle and the part of the axis contained be. naked. There are seventy-five species. tween them. This curve may be de. SENSATION. The brain is a soft pui. scribed by a continued motion, viz. bypy mass, of a whitish colour on the inside, fastening the angle of a square in the occupying all the cavity of the skull. vertex of a common parabola ; and then Minute differences are observable in the carrying the intersection of one side of substance of the brain in different parts this square and a long ruler (which ruler of it, but it is unnecessary to enter upon always moves perpendicular to the axis of a statement of them here. (See Anatothe parabola) along the curve of that pa. MY.) The spinal marrow is the continuarabola. For the intersection of the ruler tion of the lowest part of the brain, which and the other side of the square will de. passes through the great opening of the scribe a semicubical parabola. Maclaurin skull down the hollow of the back.bone performs this without a common parabola, The substance contained in the hollow of in his Geometria Organica.

the backbone is the same with that in the SEMIDIAMETER, half the diameter, cavities of the skull; and it is sometimes or a right line drawn from the centre of a convenient to comprehend both the porcircle, or spbere, to its circumference; tions under the same general name of being the same with what is otherwise brain. From the brain proceeds the called the radius. The distances, diame. nerves, which at first are fine fibres, of the ters, &c. of the heavenly bodies, are usu same substance with the brain : these ally estimated, by astronomers, in semi. fibres meet, and form soft white pulpy diameters of the earth ; and the distances cords, which afterwards spread them. of the secondary planets from their re- selves over various parts of the body, by spective primary ones, by semidiameters splitting into innumerable and exceedingof the body of the primary planet. ly minute branches. Anatomists count

Suppose the semidiameter of the earth forty pairs of nerves, (for they come off to be unity, then the measures of the sun in pairs, though they afterwards sepaand planets will be as follow : the semi. rate,) and of those nine or ten only come diameter of

from the brain at the bottom of the skull, The Earth

and the rest from the spinal marrow. The Sun

. 111 25

Those from the brain are distributed to The Moon

0.27 various parts of the head : those from the Mercury

0.38 spinal marrow are distributed over the Venus


trunk and extremities. The external or. Mars

0 65 gans of senee, the nerves, and the brain, Jupiter

11.81 are the organs of sensation. All, as we Saturn

9.77 are at present constituted, are necessary Herschel

to sensation. If the external organ is


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