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other is their fervingi as hydropbylacia or magazines of water. This is fecn throughout the World, the rivers that water all the countries inhabited or habitable arifing from chains of mountains placed in their middle, feemingly with this fole in- tent ; the Rhine* the Rhone* and the Danube, all arife from the Alps, the great refervoirs of waters in Europe. The mountains of the moon, placed in the burning lands of Africa, give rile to the Nile and Niger^ and other rivers large enough to fupply that vail and fcorched country ; and in the fame manner the river of the Amazons, and the other immenfe beds ot water neceflarv to fupply the vaft continent of South America, take their origin from the mountains called the An- des. Kircher's Mund. Subter. p. 75, feq. See the article Mountain.
We have an account of mount Vefuvius, and of the eruption from it in 1737* by the prince of Caflano, in the Philofophi- cal Tranfa&ions, N°. 455. Seel:. 1.
The matter thrown out flowed like melted lead, and moved about halt a mile in an hour, which was an unufual velocity. The trees, touched by this matter, immediately took fire, and fell. Glafs in houfes was melted into a pafte. The academy of fciences of Naples made an analyfis of the matter thrown out in this eruption. From which it appears, that this matter contains iron ; that it is fpongy at top, and tlenfe toward the bottom ; and, after growing hard, it re- tained part of its heat above a month. Damps were after- wards feen to arife in divers parts of the mountains. An am- moniacal fait, which gave an extraordinany coldnefs to water in diflolving, was alfo found here. Ibid. See alfo Seel. 2. of the faid Number.
VOLKAMERIA, in botany, the name of a genus of plants, called by Houfton, duglajjia, and paliuro affinh by Moane. The characters are thefe : The cup is a one- leaved perian- thium, of a turbinated form, very final], and lightly indented in four or five places at the end. The flower is one-leaved, and of the gaping kind. The tubs is cylindric, and of dou- ble the length of the cup. The limb is plain, and divided into five fegments, which are turned toward each fide, but gape principally one way. The ffamina are four very long capillary filaments - t the antherae are fimple. The germen of the piftil is quadrangular. The ftylc is capillary, and of the length of the {lamina, or nearly fo ; and the ffcigma is bifid. The fruit is a roundifh bilocular capfule, and in this is en- clofed a fmgle bilocular nut. Linnai Gen. Plant, p. 305. Houfton, A. A. Sloan, Hift. vok 2. f. 23.
VOLONES, among the Romans, the antient name of thofe afterwards called evocati. See the article Evoc ati.
VOLT (Cycl.) — Volt, in the manege. See the article Vault, or Volte, Cycl.
VOLTA, in the Italian mufic, mews that the part is to be re- peated one, two, or more times* according to the numeral adjective joined with it; thus Ji replica una Volta intimates to play that part once over again.
Volta is alfo a fort of dance of Italian origin, in which the man turns the woman feveral times, and then aflifts her to make a leap or jump j it is a (pedes of galliard. Brojfard.
VOLTURNAL1A, among the Romans, a feftival kept in ho- nour ot the god Volturnus, on the fixth of the calends of Sep- tember, or twenty-fixth of Auguft. Pitifc. in voc.
VOLVA, among botanifrs, a membranous matter furrounding the bafeg of many of the fungi ; and in many of them, of very lingular figure and ftrudhire.
Volva is alfo a word ufed by Scribonius Largus, and fome other authors, to exprefs the central part, or, as we call it, the core of the apple, in which the feeds are placed. He prefcrihes this in weaknefles of the flomach, and Teachings to vomit.
VOLUBLE Stalk. See the article Stalk.
VOLVENS Oculi, in anatomy, a name given by Spigeiius, and fome others, to one of the mufcles of the eye, called by Cow- per and Albinus, obliquus inferior.
VOLUNTARY {Cycl.) — Voluntary, in mufic, a piece played by a mufician extempore, according to his fancy. This is often ufed before he begins to fet himfelf to play any parti- cular compofition, to try the inftrument, and to lead him into the key of the piece he intends to perform. In the Philofophical Tranfaclions, N°. 483. Seel. 2. we have a method of writing down extempore Voluntaries, or other pieces of mufic, as faft as any mafter can play them on the organ, or harpfichord ; and that in a manner expreflive of all the varieties thofe inftruments are capable of. This is performed by a cylinder, turning equally upon its axis, under the keys of an organ, and by having points under the heads of the keys. Hence, when they are preiled down, they will make a fcratch or mark on the cylinder, which may (hew the duration of the note, and the fituatkm of this mark on the cylinder will fliew what note was touched. For farther par- ticulars we refer the curious to the tranfacKon itfelf.
VOLUNTEERS, in the military art, perfons who of their own accord ferve in the army, and at their own expence.
VOLUTA, the Volute, in natural biftory, the name of a genus of {hells, the characters of which are thefe : They are uni- valve fhells, and have an oblong mouth, with: a clavicle fometimes erecr, fometimes deprefTed ; and they are fome- 3
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times coronated at the top. See Tab. of Shells, N°. ro- This genus of metis is generally confounded by authors with that of the cylindri. There is indeed a general external re- femblance between thefe two kinds of fhclfs at firft: fight ; but when they are a little examined, they will be found very dif- ferent; The Volute are of a conic figure. One cf their ex- tremities is of a pyramidal figure, and the other formed into high ribs, which conftitute a deprefTed clavicle, or a dentatcd crown j on the contrary, the cylinder is nearly of an equal fize at both ends. And it is not neceflary to have rccourf-; to the fcflm of the mouth of this fhell, in order to fix its generi- cal character. Its figure, which is lengthened out into a point in the lower end, fufikiently character ifes this genus; and td this may be added another very remarkable character, which is, that 'the head is feparated from the body of the fhell by a high rib.
The Volutes are called by many authors, rhombi, which is a very ill chofen name, as the word expreffes the figure of a lo- zenge,; a figure very different from that of the fhell. It has been called Valuta fr©m the volute in architecture, the volutes of a capital dimtnifhing in diameter all the way to the center.; which is called the head or eye of the volute. See the article Volute, Cycl.
The moft remarkable fpecific character in this genus is in the fliape of the clavicle, fome fpecics having it very much ele- vated^ and others very flat or deprefied. The corona impe- rialism which is a fhell of this genus, is lingular in the dentated Crown, which terminates its head.
The Valuta make the moft rich and beautiful fhells of the whole body of fea productions. Rumphius calls them eximia ; and the admiral and vice-admiral fhells, fo famous among the curious, and held at fo great a price, are both of this genus. The biightnefs of the colours; the perfect, white of the enamel; and the elegant fhape of thefe (hells, would make them the firft in efteem among this clafs of bodies, even were they com- mon j but it happens that their fcarcity adds immenfely to their value. There is one of thefe fhells now in Holland* which coft the pofTefTor five hundred florins. It is from the bands and fafcise of thefe fhells, which refemble the colours of mips, that they have obtained the names of admiral and vice- admiral.
Some of the Hollanders give to another fhell of this kind the name of extra-admiral ; this refembles the admiral, but has its colours arranged without divifions of the white enamel. It isi a very fcarce fliell, but is lefs beautiful than either of the two' others.
The family of the Volutes being numerous, the fpecics may be aptly ranged under three general heads, 1. Thofe with an exerted clavicle. 2. Thofe with a deprefTed clavicle. And 3. Thofe with a coronated clavicle.
Of the firft kind we have the following fpedes : 1. The grand admiral, or archiihalajfus primus. 2. The archiiha- lajfus fecundus, or the vice-admiral. 3. The archiihalajfus arauficamis, or the orange-admiral. 4. The navel or baftard admiral. 5. The fpeclre- fhell, or concha fpeclrorum. 6. The brown lineated Volute. 7. The flame-coloured Volute; 8. The Guinea-f hell, or (peculation Volute. 9. The reddifh ftriated and fafciated Volute. 10. The punclulated Volute.
11. 1 "he Hebrew Volute. 11. The brown Volute, with two elegant white zones. 13. The lfabella Volute. 14. The vexillum. 15. The Volute, variegated with two reticulated zones. 16. The bat Volute. 17. The white Volute, with yellow fpots and lines.
Of the fecond kind, or thofe with deprefTed clavicles* we have the following fpecics : 1. The black Jeopard Volute. 2. The yellow leopard Volute. 3. The reddifh leopard Volute. 4; The chequered Volute. 5. The blue fyoitcd Volute. 6. Thei fafciated Volute, with yellow and white fpots. 7. The but- ter-tub Volute. 8. The agate-coloured ftriped Volute. 9. The yellow Volute, with a white circle. 10. The onyx vo- lute. This, when its outer coat is taken off, is of a true onyx colour, and it is in this flare that it is ufually met with in the cabinets of collectors. 11. The butterfly-wing Volute.
12. The green fpotted Volute, with two variegated fafcise. Of the third kind of Volute, the head of which is coronated, we have the following (pedes : 1. 'The crown imperial. 2. The lefs fafciated crown imperial. 3. The crown imperial^ variegated with brown. 4. The black marbled crown impe- rial. And 5* The crown imperial, called in French the metre j this feems of the texture of the web of a filkworm, only more clofely woven together. Hift. Nat. Eclair. p. 279.
VOLVULA, in natural hiftory j the name of an extraneous fof- file body, nearly allied to the entrochus, being compofed of the fame Jubilance, and being like that of a cylindric column, made up of feveral joints; the commiftures of the joints are, however, much lefs viable in the Valvule than in the entrochi, and they are not ftriated, as in the entrochus, from the cen- ter to the circumference.
The Vohula are of various figures, fome refemble in fliape a little bottle, and are called Valvule utriculata, and of thefe fome have, and others Have not, a ftar marked on their bot- tom ; others of them fwell out in the middle, and taper a little toward each end 3 and thefe, from their rcfemblance in fhape
