Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/522

Rh process, just behind the superior conchæe of the nose, or offa convoluta superiora.

The figure, size, openings, and septum of these vary greatly ; sometimes one is wanting, sometimes both are so; sometimes there are several cells without any septum, and some times the septum is placed more on one side than the other. The substance of this bone is for the most part compact, having very little diploe; and what there is of this lies in distinct parts of the bone, viz. in the thick portion behind the sella turcica, toward the symphysis with the occipital bone, and in the orbitary apophyses in a small quantity. It is articulated with all the other bones of the cranium, with the ofla malarum, ofla maxillaria, offa palati and vomer. Winslow's Anatomy, p. 26.

SPHERE (Cycl.) — A sphere is equal to four times the cone, the base of which is equal to the generating circle, and the height of which is equal to the radius. Or a hemisphere is equal to twice the cone of the same base and height. And a cylinder, of the same height and base, being triple of the cone, it follows, that the hemisphere is two thirds of the cylinder, and consequently the whole sphere two thirds of the circumscribing cylinder. Archim. de Sph. et Cyl.

The portion of a spherical surface, generated by the re-

volution of an arch ABF, about the diameter AD of a circle, is equal to the area of a circle described with a radius equal to the chord AF.

The surfaces therefore generated by arches, terminated at A, are as the squares of their chords, or as their versed sines.

Hence parallel planes, which divide the diameter of a sphere into equal parts divide the surface of the sphere into equal parts at the same time. Archim. de Sph. et Cyl.

SPHERICAL (Cycl.)—Spherical numbers. See Circular numbers, Cycl.

SPHEROID (Cycl.)— Dr. Halley has demonstrated, that in a sphere Mercator's nautical meridian line is a scale of logarithmic tangents of the half complements of the latitudes. But as the earth has been found to be a spheroid, this figure will make some alteration in the numbers resulting from Dr. Halley's theorem. Mr. Mac Laurin has therefore given us a rule, whereby the meridional parts to any spheroid may be found with the same exactness as in a sphere. We have also an ingenious treatise of Mr. Murdoch's on the same subject— [$b$ See Phil. Tranf. N$o$ 219. Mr. Cotes has also demonstrated the same proposition, Harm. Mens. p. 20, 21.] A sphere, whose diameter is equal to the great axis of a spheroid, is to that spheroid in the duplicate ratio of the axis to its conjugate. Hence the spheroid is quadruple of a cone, the height of which is the semi-axis, and the base of which is equal to a circle described upon the conjugate axis as its diameter. Mac Laurin's Fluxions Introd. p. 16.

SPHINCTER (Cycl.)— Sphincter cutanea, in anatomy, a name given by Laurence, and some others, to the muscle of the anus, called by Albinus and Winslow sphincter internu ani.

Sphincter intestinalis. See Intestinalis sphincter.

Sphincter labiorum, in anatomy, a name given by Douglas, and some others, to the muscle of the mouth, called by Riolanus and Albinus orbicularis, and orbicularis oris, and by Cowper constrictor labiorum.

Sphincter, palpebrarum, in anatomy, a name given by Molinet, and some others, to the muscle of the eyelids, called by Winslow and Albinus the orbicularis palpebrarum, and orbicularis. See the article Orbicularis.

SPHINX, (Cycl.) in the history of insects, a name given by Mr. Reaumur to a very singular species of caterpillar described in the second volume of his history of insects. The reason of the author's having given it that name, is, that when it is not eating it erects its head, and with it more than a third part of its body, into a perpendicular situation upon the leaf on which it was before laid all along; it keeps itself a long time in this situation, looking around it with a seeming air of fierceness. There are also a series of broad belts upon the body, which contribute somethtng towards its resemblance to the figure of that imaginary monster.

This caterpillar has a horn on the hinder part of its body, which seems to be of no sort of use, but merely a trouble to the creature. It is hollow, and encloses, in the manner of a sheath, the new horn which is to appear when the creature changes its skin, This the author found to be the case by cutting it several times, and always finding within it the new horn cut off also at the same place, and had often observed the great difficulty the animal had in changing its skin, when it came to the horn. Reaumur, Hist. Insect. Tom. 2.

SPHONDYLIUM, cow-parsnep, in botany, the name of a genus of plants, the characters of which are these. The flowers are disposed in umbels, and are of the rosaceous kind, being composed of several petals of a heart-fashioned shape, irregular in size, and disposed in a circular order round a cup, which afterwards becomes a fruit, composed of two large, flat, oval seeds, striated, and usually marginated at the end, and which frequently deposit their covering, and are marked with black spots on the sides where they touch one another.

The species of sphondylium, enumerated by Mr. Tournefort, are these. 1. The common hairy sphondylium. 2. The hairy sphondylium with purple flowers. 3. The great sphondylium called by authors panax Heracleum, or Herculcs's all-heal. 4. The curled-leaved sphondylium. 5. The hairy sphondylium with narrower leaves. 6. The narrow-leaved sphondylium with blackish purple flowers. 7. The little Alpine spohndylium. 8. The smooth Alpine sphondylium. Tourn. Inst. p. 319.

The common cow-parsnep, which is frequent in our meadows and pastures, and flowers in July and August, is recommended by Dr. Willis, and many others, as one of the best nervous simples our nation produces, and it is pity that it is not brought more into practice. The feed is the part in which its virtues are contained in greatest perfection, and is a very good medicine in hysteric cases, given in powder or infusion.

SPHONDYLUS, in ichthyology, a name given by Pliny, and others of the old authors, to a peculiar species of the syngnathus, or acus Aristotelis. It is the species, called by Artedi syngnathus corpore medio hexagono eauda primata; and by other authors the acus secunda species;  and by Bellonius and Gesner typhle marina. Pliny, lib. 32. cap. 11.

Sphondylus is also used by some authors, for the stones or bones found in the head of a muilet.

SPHRAGIS, the seal-stone, a name given by some authors to the single joints of the astcriæ, when found loose, not joined into a column. See the article Asteria.

Sphragis is also used by some of the old Greek naturalists, to express the spots on the back and sides of a panther. The skin of this creature is of a pale colour, and these spots are all dark and round, and look like so many regular impressions of a seal, whence the name sphragis. The Romans called any thing, that was variegated in this manner, pantherina; and we meet with the phrase mensæ pantherina, used to express tables found of some wood, which was variegated with round spots, in the manner of those sphrages on the back of the panther.

SPHYGMICA, in medicine, a term used by some for that part of the judgment of the physician, which regards the differences of the pulse,

SPHYRÆNA, in zoology, a name by which some authors have called the sudis, or lucius marinus, the sea-pike. Willughby, Hist. Pisc. p. 273. See the article Sudis.

Sphyræna altera, in ichthyology, a name given by Appian, and some other of the old Greek writers, to the esox, or common pike. See the articles Esox and Lucius.

SPICCATO, in the Italian music, signifies that every note should be well separatcd from others, and distinctly sounded. It is particularly used with regard to instruments played with a bow; and denotes that every note must have a distinct bow from that preceding, or succeeding.

SPICULUM, in Roman antiquity, a kind of weapon which some will have to be the same with the hasta, or sparus. Hosm. Lex. in voc.

SPIDER, araneus, in zoology, an insect of which we have a great number of species common among us, which all agree in the general marks and characters.

They all have weapons issuing out of the mouth, but these are of two kinds, according to the two principal distinctions of the spiders. They consist, in some, of two spiculæ, in the manner of a forked hook : this is their structure in all the kinds which have eight eyes. In others they are composed of two forcipated arms, or are divided into two claws, in the manner of the legs of a crab : these are the weapons of all those spiders which have only two eyes. The bodies of all spiders are covered with a fort of crustaceous coat, but it is tender and brittle; and in the males of all the species, the forceps, or weapons at the mouth, are larger and stronger than in the females. All spiders have two antennæ placed in the forepart of the head over the mouth : these are composed like the legs of a number of joints. The head of a spider is not separated from the shoulders by any incisure, but remains fixed to them as all of one piece.

The eyes of the spider differ greatly in number, situation and figure, in the different species; and sometimes the different eyes of the same spider are of different sizes. All spiders have eight legs, which are all inserted into the breast, but in the length and figure of these there is as much variety as in the eyes in the different species of