Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/736

 UNI

Vol

fcvcral varieties of fhapes It is found in, and trying it by the feveral tefts which fix the criterions of foffils, has determined it to be no other than a terrene cruftaceous fpar, not very dif- ferent from me ofteocolla, and other bodies of that genus, which he has called the cibdelopla'cia ; and has diftinguifhed this peculiar fpecics by the name cibdeloplacium albido-jubcine- teum, friablle fuperfcie lav'i, or the whitifli-grey friable crufta- ceous fpar, with a fmooth furface.

It differs principally from the ofteocolja in its foftnefs and the fmoothnefs of its furface; but from its having, like many other of the cruftaceous terrene fpars, the property of encruft- ing, and fometimes even permeating the pores of bodies, and in a manner petrifying them, it has obtained the names of the things it thus lodges itfelf in and about, which being ufually bone, and fome of them bones of an extraordinary fize and figure, have been taken for the bones and horns of Uni- corns ; and the name and nature of the body itfelf wholly loft and neglected, and that of the horn, with that of its imaginary animal, only preferred.

They are, however, now fenfible in Germany, that it is not the horn, but this fubftance which is lodged about it, which is the medicine; for they never ufe the fofEIe bones, which are petrified in the common wav, but only fuch as are im- pregnated with this fparry fubftance ; and even ufe all fub- ftances whatever, which are impregnated with this, whether bones or wood, under the fame name, calling the natural tu- bular pieces of it, which are very common, and alio the pieces of branches of tree impregnated with it, by the common name of Unicorn's bom, while they allow plain bones, petri- fied in the common way, no fuch name. So that the word is now become a mere technical term, and fignifies either this fpar in its pure ftate, or any fubftance whatever which is im- pregnated with It.

It is a lax and fpongy terrene fpar, and is naturally of a regular form, in fome degree like that of the ofteocolla, being always found, where it has concreted pure and not been in the way of any extraneous fubftance, an oblong and moderately thick cylindric tubular body, frequently narrower at one end than the other, and approaching to a conic form. Ufually its hollow is empty, but fometimes it is found filled up with a fubftance of the fame nature with itfelf, only compofed of a larger proportion of earth with lefs fpar, and therefore more crumbly and foft. Thefe are found of various fizes, from an inch to three feet long. The larger fpecimens are molt fre- quent. And it is very probable, that the ignorance of the

• firft ages, which brought it into ufe in medicine, might take thefe natural concretions for Unicorns boms. Jt is found in other parts of the world befide Germany, and is in great efteem in many places as a fudorific and aftringent; and is given in fevers, attended with diarrhceas, with great fuccefs. Hilt's Hift. of Foff. p. 361.

UNIFORM (Cycl.)— Uniform Matter, in natural pbilofo- phv, that which is all of the fame kind and texture.

UNILOCULAR CapfuU, among botanifts. See the article Capsule.

TJNISETA, in natural hiftory, the name of a fpecies of fly, found frequently fitting on the ammi or bifhops-weed, and inguifhed by having one long hair or briftle growing out at its tail. See the article Henothrix.

UNITE, in the manege. A horfe is faid to unite, or walk in union, when, in galloping, the hind quarters follow and keep time with the fore. See the article Sinew.

UNITY (Cycl.)— It is to be obferved in algebra, that Unity itfelf has three different expreffions of its cube root, one real, and the other two impoffible or imaginary. Thus the three cube rootsf.fi, arei, ~ I +v / — 3 ^ n d — * — y/ — 3

2 2

This is fometimes of ufe in finding the cube roots of quanti- ties, appearing under impoffible expreffions. See Maclau- rin's Algebra, p. 128. feq.

The two impoffible expreffions of ^ 1 may be thus found : Let x = 1 then #3 — 1 0F x 3 — 1 — and x — 1 = 0. Divide #3 — 1 by x— 1 the quotient is xx + x-\- 1 = 0. Or xx -f x = — 1 refolve this quadratic equation, by adding £ to both fides. Then w + *-|-^=: — 1, and extracting

the fquare root, x -f- i = y' -

±y-

i±tf-

V-3

That i:

Therefore x =

and x = -

V-3

See Maclaurin, lib. cit. p. 226.

UNIVALVE Shells, in natural hiftory, a term ufed to exprefa one of the three general claffes of fhell-fifh ; the other two are the bivalves and multivalves. The univalve fhells are thofe which confift only of one piece, not of two or more joined together. Of thefe univalve fhells, nature affords a very great variety ; fo that they are aptly diftributed by a late French author into fifteen diftinct genera. Thefe are, 1. The patella:, or limpets. 2. The patella plana:, called alfo auris manna, the' ear-fhell. 3. The canales, or tu- buli marinty the fea- tubes. 4. The lunar cochlea?, or round-mouthed mails. 5. The cochlea femilunares, or fnails with femicircular mouths. 6. The cocbk* ere ds-

prejfi, or flat-mouthed fn.uk. j. The navicular or boat- ftieils, commonly called nautili of nautilus. 8. The buc- cina, or trumpet- fhells, 9. The turbines. 10. The va- luta. 11. The rhombi. 12. The murices. 13. The purpura. 14. The concha globofa. And 15. The por- cellana, each of which fee under its proper head, Patella, Ay ris Mdrina, &c, Hift. Nat. Eclairc. part 2. p. 235.

UNIVERSAL (Cycl.) — Universal Equinoctial Vial. See the article Rwo-Dial, Cycl.

Universal Problem. See thearticle Indetermined Pro- blem, Cycl.

UN POCO, in the Italian mufic, is often put before the terms. allegro, adagio, prejlo, piano, ckc. Where it fhews that the movement, with their direction, is fomething lefs than it would otherwife have been, had this word been omitted. Thus allegro ihews that the movement is to be made in a brifk and gay manner ; and Un poco allegro the fame, only in an' inferior degree, and fo of the reft.

But if pin is put between Un poco, and the above-mentioned terms, then their ufual fignificatton is a little increafed, as Un poco pin allegro fignifies a little more brifkly than allegro- alone requires. The contrary of this happens if, inftead of pin, the word men, oimeno, be ufed, as Un poco meno allegro, 1. c. a little lefs gayly than if allegro were alone. See the ar- ticles Allegro, Adagio, Presto, bV.

VOARCHADUMIA, a kind of cabala, or enigmatic art, re- lative to metals, which propofes the exultation ofgi.ld by ce- mentations, and other methods ; among which charms made of the Hebrew letters have their place.

VOCA, in ichthyology, a name given by Gaza, and fome other writers, to the fifh called boops by the generality of writers. It is a fpecies of the fpari, and is diftinguifhed from the reft by having four longitudinal parallel lines, of a bright yellow and white colour, rcfembling gold and lifver on its fides. See the article Sparus.

VOCATORES, among the Romans, were fervants whofe b*u- finefs it was to call theguefts, receive them, and affign every one a place according to his dignity. Pitifc. in voc.

VOCE Sola, in the Italian mufic, denotes a piece compofed for a fingle voice, generally accompanied with a thorough bafs on the harpfichord or organ, without other inftrumems. But 'if befides that it is to be accompanied by other inftrurnents, they add, con violini, with violins ; due violini, e violoncello, e bajfo per Vorgano, i.e. with two violins, a bafs violin, and a thorough bafs on the organ ; con violini ojlromcnti, i. e. with violins, or inftruments ; parti, con parti fenza violini, i. e„ part with, part without violins, &c.

VIOLATICA, in medicine, a name given by authors to a fort of wandering pain, attended with a tumor, and affecting, at different times, different parts of the body ; it is by fome' ac- counted a fpecies of the fcurvy ; by others, of the leprofy.

VOLATILE Salts, It is the opinion of inar.y cf the greateft chemifts, that our diftinffion of falts into fixed zud volatile, is far from juft, for that there are in nature no fuch thing as fixed falts.

Tartar is generally allowed to contain as much fixed fait z% any thing, yet this fubftance, treated by fermentation, in Langeloi's method, yields all in volatile fait that it would otherwife have yielded in fixed, and leaves fcarce any fixt at all. The fame procefs will have the fame effect on the fuppofed fixed faks of moft other fubft ances ; and upon this, and many other confederations, it appears highly probable, that ourdivifion of faks into fixed and volatile is unknown to nature ; there not being to be formally found in any' body, before calcination, any fixed fait; but falts are in themfelves all volatile, though by the action of the fire they are apt to be colliquated among themfelves, and blended with the earthy parts, and by that means rendered fixed. The divifion of falts into acids and alkalis has much more reafon for its foundation; Thefe are differences which really exift in them, and by means of thefe all fermentations, and all motions in natural things begin. Both thefe faks appear to be in their own nature volatile, and therefore eafily lefbluble- by the fupervening fait of the air.

It appears that all vegetables, efpecially the aromatic clafs, if they are any confideiable time expofed to the air, lofe their falts. The foundeft wood, lofing its falts in procefs of time,, in the fame manner moulders away.

Thefe are proofs that the falts of thefe bodies are in themfelves volatile, though they are all liable to be rendered fixed by the action of fire, by which means the acid and the alkali ara blended together, and the mixture becomes fixed. There is an old axiom among the chemifts, that things vola- tile are rendered fixed by fuch things as are fixed ; and thofe fixed are rendered volatile by fuch as are volatile; but it ap- pears from thefe proceffes, when rightly uiiderftood, that this is an erroneous maxim, that two volatile things may fix one another ; and two fixed things may become volatile toge- ther, according to the nature cf the proceffes by which they are treated. The common traders in timber are well ac- quainted with thefe properties of the falts of wood, though they know not the reafons of them ; and as the air or fire may alter or drive off the falts of timber, and fo render it lefs firm and ftrong, they fink fuch pieces under water as they would 3 prefer vc-