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proper nutritious matter, fince the ftony particles they find there are much of the nature of their natural fliells in the fca. , . . -
The growth of the foffile fliell from its femmium is fup- pofed, by thefe writers, to be inftantaneous, not progreffive ; and the reafon they give for this is, that there is abundant matter for the formation of it in readinefs altogether. They advance, that it is not at all more difficult for nature to form a (hell from fuch zfeminium in the earth than in the fea, provided all the neceflary requitites are in readinefs, which they fuppofe, in this cafe, to be plainly the fact ; and they difallow the analogy between the formation of thefe bo- dies and crvftals, becaufe they obferve that thefe are formed from femlma, thofe only from apportion of particles. They alfo obferve that thefe (hells, as they are formed in the earth, can never have been inhabitants of the fea in that form, becaufe they never have any thing truly of the nature of fhelly matter about them. 'This is, however, abfolutely an error. The foffile nautili have ufually a great deal of the true pearly matter of the fliell about them, and all the argu- ments, given in favour of this ftrange hypothecs, feem as eafily confuted. The reader has an opportunity, however, of examining this fyftem in its full force ; and on compar- ing it with the diluvian fyftem, delivered under the article of Ficvreu Jones, will be able to judge whether the prefent age be in the right or not, in giving the preference to that fyftem. Langli Hift. Lap. Fig.
SEMIORBICULARIS labiorum, a name given by Winnow, and others, to the mufcle called by Albinus orbicularis oris, and by others conjlrioior, and fpbiniier labiorum.
SEMIREVERBERATORY fire, in chemiftry, a term ufed to exprefs fuch a reverberatory fire, in which the flame is only beaten back upon the bottom of the veflel.
SEMIS, among the Romans, the half of the as. See the ar- ticle As, Cyd.
SEMISICIL1CUS, a word ufed by fome pharmaceutic writ- ers to exprefs a drachm.
SEMISIDERATUS, a word ufed by fome for a perfon ftruck with a hemiplegia.
SEMI-SOSPIRO, in the Italian mufic, a little paufe, of the eighth part of a bar in common time. See Pause, Rest, Character, Cyd.
SEMI-SPINAUS, a mufcle, called alfo tranfverfo-fpinalis dorfi. It is a flefhy mafs, which, from all the fpinal and tranfverfe apophyfes of the back and loins, is extended in diftinct fafciculi over the vertebrae themfelves. It is made up, like that of the neck, of feveral oblique converging mufcles, the uppermoft. of which is fixed below to the third tranfverfe apophyfis of the back, and above to the firft fpinal apophyfis. The loweft is fixed below to the third tranfverfe apophyfis of the loins, and above the laft fpinal apophyfis of the hack. They are divided by anatomifts in- to the external, which are firft difcovered, and the inter- nal, which lie immediately on the vertebrae. The external, from the firft vertebra to the feventh inclufively, appear to be longer than the internal, which are covered by them. Winjlffu£% Anatomy, p. 248.
Semi-Spin alis colli, a mufcle, called alfo tranfverfo-fpinalis colli, and taking into its compofition all that flefliy mafs, which lies between the tranfverfe and fpinal apophyfes, from the fecond vertebra of the neck to the middle of the back, under the fplenius and complexus major. It is compofed of feveral oblique converging mufcles, which may be divided into external and internal, of which the external are the longcft. Thefe are fixed below to the tranfverfe apophyfes of the fixth, feventh, eighth, or ninth vertebrx of the back, by tendinous extremities, which as they afcend become flefhy, and mix with each other. Their fuperior infer tions in the neck are fix in number, whereof the firft, which is tendinous, is in the feventh fpinal apo- phyfis, and the others, which' are flefhy, are in the five next fpinal apophyfes. The internal are fhorter, and more ob- lique than the external, and are partly covered by them. They are fixed, by their lower extremities, to the tranfverfe apophyfes of the three or four upper vertebrae of the back, and to the oblique apophyfes of the four or five lower ver- tebrae of the neck, and by their other extremities, they are inferted in the fix fpinal apophyfes of the neck. Some of thefe internal mufcles are very fliort, lying wholly between the fpinal apophyfes, and the oblique or tranfverfe apophyfes next them. Winfiott/s Anatomy, p. 243.
SEMISPINATUS, {Cyd.) in anatomy, a name given by R.10- lanus, and fome others, to the mufcle, more generally known by the name of longiffimus dorfi.
SEMITALES, among the Romans, a name given to the Gods, who were the protectors of roads. See Hift. de l'Acad. des Infcrip. Vol. 2. p. 22.
SEMI-TONE, {Cyd.} in mufic, is of two kinds, diftinguifh- ed by the addition of greater and lefs. The firft; is ex- prefled by the ratio 16 to 15, or £f ; and the fecond by 25 to 24, or 11. Thefe two are fo far from being nearly equal, - as it is faid in the Cyclopaedia, from Malcolm, that they differ by a whole enharmonic diefis ; which is an interval practicable by the voice b , and was much in ufe among the
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antients, and not unknown even among the modern practi- tioners c . — [° See Diesis. e See Handel's Oratorio of Samfon, in the fecond part of the fong, Return, return, Q God of hop.']
Semi-tone major.-~-The octave contains ten femi -tones ma- jor, and two diefes, nearly; for the meafurc of the octave being exprefted by the logarithm i.ocoooo, the femi- tone major will be meafured by 0.093109. Euler, Tent. Nov. Theor. Muf. p. 107. See Interval.
Semi-tone minor. — The octave contains feventeen femi-tones minor, nearly. If the meafure of the octave be the loga- rithm i.cooooo, the meafure of the femi-tme minor will be 0.058894. Euler, Tent. Nov. Theor. Muf. p. 107. See the article Interval.
SEMIVULPA, in zoology, a name by which Gefner, and fome others, have called the cfofifum- See Opossum.
SEMODIUS, among the Romans, a meafure equal to half the modius, or the fixth part of the amphora. See Mo- dius and Amphora, Cyd.
SEMONES, among the antients, a clafs of Gods that were of a middle nature, between the celeftial and terreftrial Gods. Juftin Martyr has miftaken one of thefe for Simon Magus. Mem. de l'Acad. des Infcrip. Vol. I. p. 270.
SEMYDA, in botany, the name of a tree, mentioned by Theophraftus, and by fome fuppofed to be the fame with the betula, or birch tree, but very erroneoufly. Gaza indeed has tranflated the word by betula, and moft of the later authors having confulted only the Latin tranfiation, in their references to this author, have taken it upon credit that he meant the birch by this name.
Theophraftus fays that the famyda, or femyda, has a leaf like the walnut tree, only fomething narrower; now that the betula, or birch tree, has no fuch leaf, every one muft know that ever faw it. He fays alfo, that the bark of the femyda is variegated. This as little agrees with the betula, as the ufe he fays was made of it. It was efteemed the lighteft of all woods, and therefore cut out into all things that required ftrength without much weight. The ufe of the birch in rods for malefactors, is as old as any thing we know ; and had it been the birch that the author was here defcribing, he would not have omitted this ufe.
SENA, in botany, the name of a genus of plants, the cha- racters of which are thefe. The flower is of the rofaceous kind, being ufually compofed of five petals, difpofed in a circular form. The piftil finally becomes a pod of a flatted fhape, ufually fomewhat crooked, and compofed of two membranes, between which are lodged feeds, refembling grape ftones, and divided from one another by thin parti- tions. See Tab. 1. of Botany, Clafs 21. The fpecies of fena, enumerated by Mr. Toumefort,. are thefe. 1. The Alexandrian fena with fharp pointed leaves. 2. The Italian fena with obtufe leaves. And 3. the privet- leaved American fena. Tettrn. Inft. p. 618. The purgative virtue of this plant is found, though very different in degree, in infufion, according to the manner in which that infufion is made. In a cold infufion it purges very gently, but this, according to the time it remains in the water, is different in degree ; and in a warm infufion it purges much more brifkly. It is eafy to fee from this, that its operation is very difficult to afcertain, fince the decree of heat, which it is not eafy to reduce to any certainty, makes it ftronger or weaker, though the quantity of the medicine be the fame, and the variety of its effect depends on the manner in which it is penetrated by the water, which is to diflblve its active principles. It is obferved that the follicles, or pods of fena, operate more gently in infufion, than the fena itfelf; the reafon of this is, that the texture of thefe pods is much more firm than that of the leaves, and therefore the water penetrates lefs into it, and extracts lefs of its active principles. It is certain that thefe pods are equally purgative with the leaves, nay every part of the plant is fo ; the very ftalks, or pedicles of the leaves, having as much virtue as the reft, but only requiring a longer time to boil, to communicate it to water, becaufe of their clofer texture. See the article Infusion.
The moft certain way, therefore, of giving this medicine is in the form of Mr. Geoffroy's dry extract, which is made of a very ftrong infufion, evaporated to a dry and pulverif- able fubftance, eafily taken, and of no ill tafte, and which operates in a very finall quantity, one third part containing the virtue of the whole, or nearly fo ; the niceft calcula- tions fhewing, that twenty four grains of the extract, fome part of which may be fuppofed to be earth, or other acci- dental or ufelefs matter, poftefTes the virtues of a drachm in fubftance. Mem. de l'Acad. des Scienc. Par. 1738.
SENATE (Cyd.) — It has been a queftion among the learned how fenators were created, and how the vacancies of the fe~ nate in old Rome were fupplied.
Dr. Middleton is of opinion, that the conftant and regular fupply of the Jsnate was from the annual magiftrates ; who, by virtue of their feveral offices, acquired an immediate right to fit and vote in that aflembly. The ufual gradation of thefe offices was that of quxftor, tribune of the people,
aedile,
