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the bafis of fea fait,, that there fhould be found Come places in the world where this bafis may have concreted of itfelf, without any of that acid being near, which would have

' made it common fait, and that it therefore remained in the flate of the bafe alone, and conftituted this natrum. The other is alfo accounted for on the fame principles, it being the fait produced by burning from a common jea plant, which muft have imbibed a vaft quantity of jea fait, and which may have been decompofed in its vefTels, and left us only the bafe without the acid ; which bafe cannot therefore but appear on the burning the plant, and evaporating water which had been poured upon its allies. This accurate account of Mr. Du Hamel's gives us a very perfect idea of what was, however, no new difcovery in him fince Stahl had before affirmed this alkali to be the ba- fis of fea fait, though he had wrapt up his meaning in fo much obfeurity, that it would never perhaps have been per- fectly underftood, without Mr. Du Hamel's affiftance. Mem. del'Acad. Par. 1736. See Salt.

Se a find. This is one of the beft improvements for many forts of land, and if rightly underftood by our far- mers, might be of almoft univerfal ufe; moft of our fhores are covered with it, where it is unregarded, and there are few places where it might not be had by water carriage. This fond is not of the nature of the common fend found in our pits, nor indeed properly to be called by that name, though it will be heft underftood by it among the people whofe ufe it is recommended to. It is the fragments of fea fhells beat to pieces againft the fhore, and ground almoft to powder by the waves continually wafhing upon it. It is fometimes compofed of fhelly matter alone ; but fometimes it is made up partly of this, and partly of broken ftones : jn this laft cafe it is called Jbelfy fa'id, and is not much cfteemed. See Sand.

In Cornwall they ufe this with great advantage, and have it of three colours. About Plymouth it is grey, or bluifh, like afhes, which is owing to its being in great part made up of mufcle and oifter fhells. Weftward, near the Land's End, it is white; and in Scilly gliftering, from a mixture of fome fpangles of talc among it. This laft kind is made of the powder of fcallop fhells, and of the mouldering of a fort of moor ftone, or white granite, not fo hard as the common kind, and containing, like it, a large quantity of talc. On the northern fide the fand is rich, and of a brownifh or red- difii colour, and is principally compofed of the broken fhells of cockles ; and it owes that colour to the wafh of the Se- vern, which falls foul and dirty with a yellowifh mud into the Severn fea.

Befide thefe differences in the colour of the fand, there is alfo another difference, which is in the largenefs or fmall- nefs of the grain. In many places the different parts of the fame more afford a larger and a fmaller fort, and thefe are chofen according to the fcveral occafions. The fmalleft fort gives its virtues out the fooneft, but the large kind keeps the land in heart for the longeft time together : the tenant there- fore is always beft pleafed with the fmaller, and the landlord with the larger. Philof. Tranf. N° 113.

Sea Jicknefs is faid to be prevented by drinking^ water mix- ed with wine.

Sea fwallowy the name of a bird of the lams, or gull kind, called by authors jlema, and common on our coafts. See the article Stema.

^ a -turtle- do- -e, in 7,oo!ogy, the name by which we com- monly call the little diver, called by Mr. Ray columba Green- landica.

It very much refcmblcs the coulterneb, or anas arclica of Clufius, only it is much fmaller, and its legs are red, and it has no hinder toe- Its beak is long, not compreffed, or flatted fideways, as in that bird, and a little crooked and iharp at the end. It has a large white fpot on each fide of the forepart of its head, and excepting that it is all over black. Rafs Ornitholog. p. 245.

Sea water. See the article Water.

SEAH, in Jewifh antiquity, a meafure of capacity containing fix cabs. See Cab.

SEAMS (Cycl.) — Seams ofajhip, are places where her planks meet and join together. There is alfo a kind of peculiar feam in the fowing of fails, which they call a monk's feam.

Seams of a fail, are of two forts, monk's feam, and rottnd- feam. See Monks, &c.

Round Seam, of a fail, is fo called, becaufe round like the common feam.

SEASIN, or Seasing, in a fhip, the name of a rope by which the boat rides by the fhip's fide when in harbour, &c.

SEAT (Cycl.) — Seat, in the manege, is the pofture or fixa- tion of a horfeman upon the faddle.

To feat a horfe upon his haunches or hips, fee the article Put. r

SFB, a word ufed by fame chem'ifts to cxprefs gold, and by others for alum.

SEBAR, or Cebar, in the materia medica, a name by which the Arabians call the lignum aloes, or alee wood, a perfum- ed aromatic drug. Suppl. Vol. II.

SEBEL, an Arabian name for the diforder of the eye, ufually called a pannus.

SEBESTENA, in botany, the name given by Dillcnius to a genus of plants called cordia by Plumier, and under that name characferifed by Linnaeus. See Cordia.

SECACUL, in the materia medica of the antients, a name gi- ven by Avlfenna, Serapion, and others, to a root which was like ginger, and was brought from the Eaft-Indies, and ufed as a provocative to venery.

The interpreters of their works have rendered this word iringo, and hence fome have fuppofed that our eryngiurr, or eryngo, was the root meant by it ; but this does not ap- pear to be the cafe on a ftricl enquiry, and there is fome reafon to believe that the famous root, at this time called ghfeng, was what they meant.

SECALE, rye, in the Linmean fyftem of botsnv, makes a diftincf. genus of plants, the characters of which are thefe* The cup is a cafe or cover, compofed of two valves, and con- taining two flowers. The valves are ftrair, erccT:, and placed opnofite to one another ; and are fharp pointed, and fmaller than the leaves of the flower. The flower is bivalve ; the outer valve is rigid bellied, pointed, fomewhat compreffed with a nm upon its lower edge, and is terminated by a long awn or beard : the interior valve is flat, and pointed* The ftamina are three capillary filaments, hanging out of the flower. The antherse are oblong, and fplit at the ends. The germen of the piftil is of a turbinated form. The ftyles are two, reflex and hairy. The ftigmata are fingle. The flower clofely wraps up the feed, and when it is ripe opens, and lets it out. The feed is (ingle, oblong, fomewhat cv- lindric, naked, and pointed. Linnai Gen. Plant, p. 17.

SECAMONE, in botany, a name by which the Egyptians call a fpecies of periploca common there, and difHnguifhed by Mr. Tournefort by the name of periploca fblfis cblongis angujlioribus, the long narrow leaved periplcca. See the article Periploca.

SECESPITA, among the Romans, a knife with a round ivory handle, adorned with gold and filver, which the flamins and priefts ufed at facritices. Pitifc. in voc.

SECIUM, among the Romans, a term ufed to fignify every thing the priefts cut with the knife fecefpha, as the libum, placenta, &c. See Li bum, c5V.

SECLIA, a name by which fome authors have called worm- wood. See Santonicum/^w«.

SECTINEUS, a fmall, flat, and pretty long mufcle, broad at the upper part, and narrow at the lower j fituated obliquely between the os pubis, and the upper part of the os fe- moris.

It is commonly a fingle mufcle, but is fometimes found dou- ble. It is fixed above by flefhy fibres to all the fharp ridge, or crifta of the os pubis, and to a fmall part of the oblong notch, or depreffion on the forefide of the crifta, in which the upper extremity of this mufcle is lodged j from thence it runs down* obliquely towards the little trochanter, under, and a little behind which, it is inferted obliquely by a flat tendon between the fuperior infertion of the vaftus internus, and inferior infertion of the triceps fecundus, with which it is united. JVinfow's Anatomy, p. 206.

SECOMLE, in natural hiftory, the name of a genus of fof- fils, of the clafs of the feptaria, the characters of which are ; that they are bodies of a dufky hue, divided by fepta, or partitions of a fparry matter, into feveral more or lefs re- gular portions, of a moderately firm texture, not giving fire with fteel, but Fermenting with acid menftrua, and eafily calcining.

The feptaria of this genus are, of all others, the moft com- mon, and are what have been known by the little expreffive, or miftaken names of the waxen vein, or ludus HelmontH. The Englifh name was acquired by the likenefs of the body of the m;ifs in fome of the fpecies, and of the fepta in others, to yellow wax: and the Latin one was owing to this, that the famed Paracelfus, who had the cubic pyritse in treat efteem for diffolving the ftone, called thofe bodies, from their refembling a die in fhape, Indus; and Van Hel- mont afterwards miftaking the bodies of this genus for the ludus of Paracelfus, gave them in the fame cafes, and called them by the fame name.

We have many fpecies of thefe bodies common among us. Of the whitifh or brownifh kinds we have thirteen j of the yellowifh five ; and of the ferrugineous ones four. Of the white or brownifh kinds are, r. A brown one, ex- ternally crey,with yellowifh white fepta. This is very com- mon in (jermany, and the chemifb and apothecaries there, who ufe it as a remedy for the ftone, always choofe this fpecies. We have it alfo common among us, and that in the neighbourhood of London ; the clay-pits behind Gray's Inn Lane, and about Iflington, affording it in great abundance. 2. A hard brown one with fewer fepta, common in the fame places with the former. 3. A hard blackifh brown one with whitifh partitions. This is a coarfer, and much lefs beau- tiful kind than any of the former, and generally lies near the furface. It is common about Pancras, and in many other places. 4.. A hard brownifh yellow one, ■ with ■ yellowifh

i 2 D d d • white