Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/709

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and are very different in the different falts, and in moft. of them very beautiful.

This gentleman acknowledges that the obfervation was owing to accident ; for having fet out feveral fmall veflels full offblu- tions of falts, in order toobfervethe progrefs of their Vegetation, he was greatly pleafed and furprized to find this remarkable accident attending them. The firft fait he obferved it in was nitre ; but foon after, finding that the folution of fal armoniac did the fame, and that with different- figured concretions, the figures which the reft would affume appeared to deferve an enquiry. He chofe to call thefe figures, not before obferved, Vegetations, in the language of the chemiffs ; not that he fup- pofed them to be produced as plants, by a regular afcent of juices, but merely by appofition of faline particles one to ano- ther. Thefe are all properly of the third clafs of the chemi- cal Vegetations, according to Mr. Homberg's diftin&ions. The feveral falts he chofe to experiment upon, were refined falt-petre, fal prunella;, fal armoniac, fea-fak, fal ex duobus, or the impregnation of the caput mortuum* left after the diftil- lation of aqua-fortis, cifi:.

Thefe falts were diffblved in the feveral following liquors ; common water, lime water, white wine, red wine, fpirit of nitre, fpirit of fait, fpirit of vitriol, oil of tartar per deliquium, fpirit of fait, and the volatile fpirit of urine, and mixtures of oil of tartar per deliquium, with fpirit of vitriol, and with fpirit of nitre.

Salt-petre, diffblved in common water, produced Vegetations refembling the rugged points of rocks ; and the more the wa- ter is faturated with this fait, the more beautifully the Vegeta- tions 2re formed : For this purpofe, one part of fait may be diffblved in three parts of water, in warm weather ; but in colder weather the proportion of the water muft be increafed to four times, or four and a half, the quantity of the fait. Salt-petre, diffblved in Kme-waterj affords the fame Vegetal tion ; but the points are finer, and the whole bodies of- the 1 concretions fmaller. Wine diflblves a fmaller quantity of falt-petre than water ; and though the Vegetations are fmaller from this folution, yet every particle ctfmpofing thefe is gra-' nulated in manner of the furface of a mulberry ; and the whole concretions refemble fome of the botryoide mineral bodies in miniature, or grapes thick fet upon the bunches. Spirit of nitre, and oil of tartar, being mixed together to' the point of faturation, and the fait formed by this diffblved in a quantity of water juft fufficient for this purpofe, and the folu- tion expofed in a glafs or earthen veffel to the fun, there are formed concretions of the fame kind with thofe of the com- mon falt-petre diffblved in water, except that they are more fine and more ramified. It need not appear wonderful, that this mixture fhould produce the fame concretions with pure nitre, fmce it is well known, that true and proper nitre is the refult of it.

An ounce of crude fal armoniac being diffblved in three ounces of common water, and expofed to the fun, there form, upon the edges of the veflel, Vegetations more thick and lefs pointed than thofe from nitre, and more refembling rude mafles of ffints thrown confufedly one upon another. This folution be- ing fet out in veflels of tin, the appearances are much altered, the concretions are all of a roundifh figure, and are covered on their outfides with numbers of fine points. The fame fait, diffblved in lime-water, produces a different fort of concretion ; thofe in glafs veflels are compofed of round heads, befet with feveral tolerably large points ; and in veflels of other kinds, the concretions vary a little, but al- ways keep the fame general form.

Spiiit of fait, and fpirit of urine, mixed to the point of fatura- tion, and expofed in earthen veflels, produce concretions very little differing from thofe of fal armoniac, when they are nicely examined ; on a carelefs view, however, the)' appear very different, the feveral granules they are compofed of being much fmaller than in the common folution of that fait. It is not ffrange that this mixture produces thefe concretions, as well as the fimple folution of fal armoniac, fince this mix- ture produces a true and genuine fal armoniac. Sal armoniac diffblved in white or red wine, and expofed, produces, inftead of thefe roundifh concretions, a fort of ob- long ones, fomewhat irregular in form, and granulated ali over their furfaces, in the manner of a mulberry. Thefe are fattened to a fort of tails, and by this means are made to re- femble, upon the whole, clufters of grapes. This might give perfons of warm imaginations an opinion, that the wine was ihewing itfelf again in the form of the grape, whence it was made ; but it is to be obferved, that the flowers of fal armo- niac, winch rife in the diffillation of the volatile fpirit with fait of tartar, being diffblved in water, produce the fame grape-like clufters. And the common fal arrrioniac, diffblved in an impregnation of the caput mortuum of aqua-fortis, af- fords the fame grape-like concretions as when diffblved in wine.

The concretions of thefe falts will form themfelves in the {hade, but they are always, much more beautiful when the veflels have been expofed to the (un ; they are alfo much fooner formed by affiftance of the fun's heat : It will take a month at leaft: to produce -.rood Vegetations of cither in the Si'ppt, Vol- II.

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made; but in the furi, a week, or, at the utmoft, fen of twelve days, will be found fufficient. There are many folu^ tions of falts, however, which have no occafion for the fun's heat to form them. Of this kind are the following : A mixture of fpirit of vitriol, and oil of tartar per^deliqumrnj being made up to the point of faturation, add fo much water as will be fufficient to diffolve the fait precipitated to the bottom of the mixture; if this folution be fet to vegetate^ the concretions will form themfelves into a fort of little bufhes : Thefe are very beautiful ; but fo many accidents muff concur to their formation, that they will not always appear, even frOrri the fame quantities of the ingredients, managed feemingly in the fame manner.

One of the moft ready and moft beautiful of all the faline Ve- getations, is that formed by a folution of the falts in the caput mortuum of aqua-fortis, with common water. If a pint of water be put to half a pound of this caput mortuum, and the whole boiled together, that the falts may be diffblved, and the liquor afterwards filtrated, and expofed iri an earthen veflel there will be formed, if) about eight and forty hours, Vegeta- tions wholly like thofe from the mixture of fpirit of nitre and oil of tartar, except that thefe from the caput mortuum are more ramified and more beautiful. When the folution is ex- pofed in a glafs veflel, they form themfrlves on the furface Into very beautiful figures of trees, fhrubs, and bufhes ; and this not only on the furface, but on both the infide and outfide of the glafs, Thefe can be compared to no known concretions except to the Vegetations of iron, defcribed by Mr. Lemery; they differ indeed in nothing from thefe, but that the Vegeta- tions of. the metal are of a brownifh colour, whereas thofe of the fait are white;

This impregnation fucceeds beft in dry weather, for in a nioifl: feafon the Vegetations form themfelves more flowly, and are much lefs beautiful: Glafs veflels are alfo eflential to the Vegetations being formed in their greater! beauty ; they are ne- ver nearly fo beautiful in earthen ones ; and even in the former the Vegetations fucceed much better in fome forts of glafs, than in others. The caput mortuum of aqua-fortis alfo is very dif- ferent, from the different diffillations ; and all of it does not fuc- ceed alike in this Vegetation of the fait. That which looks lighteff, and of the reddeft colour, feems the beft for this pur- pofe. An impregnation of this caput mortuum in red wine,- produces no Vegetations, but only forms a cruft with fmall eminences on the fides of the veflel ; and falt-petre, diffblved in the impregnation of this caput mortuum in water, pro- duces a much more beautiful Vegetation than that of falt- petre alone ; but at the fame time much lefs beautiful than that of the impregnation alone. Sca-falt, diffblved in the fame impregnation, fometimes will produce beautiful Vegeta- tions, but fometimes only a rough cruft. Common rough falt-petre forms no Vegetations, but only crufts over the vef- fel, as is the cafe with the folutions of many of the metals in different acid menftruums. And the fame is the cafe in regard to many falts from which it might be natural to expect con- cretions of this kind. Memoirs Acad. Par, 1/22.

VEGI, or Uci, the names given by the Arabian phyficians to the acorus. Thefe writers feem not to have been acquainted with the plant itfelf in its growing fiate, but only to have known that part of it which was ufed in medicine in their time; but the Greeks defcribe the plant in fome fort. Serapion mentions the Vegi or acorus as a medicine ; but he quotes no one Arabian who has named it, but tranferibes his account of it from Diofccrides ; and Avifenna fays it is the root of a plant much refembling the alburdi, that is, the pa- per-reed of the river Nilus. Avifenna adds, that the acorus grows only in wet places ; and the old manufcripts of Diofco- rides have the epithet papyraceum for the acorus, though im- perfectly exprefied ; and thence probably this author took the hint of refembling it to the paper-reed;

VEIENTANA Gemma, in natural hiftory, the name of a gem defcribed by Pliny, and faid to be found in Italy ; he fays it was black, but furrounded with a circle of white ; it was pro- bably a ftone of the camea kind.

VEIN (tyci.)-Pulfations of the Veins. The pulfatiorfs of the arteries are well known ; but though no fuch motion be natural to the Veins, yet there have not been wanting in- ftances in which a morbid ftate has been able to produce them; The pulfations of the arteries anfwer to the motions of the heart, tbat throws the blood into them ; but when this fluid has once got into the Veins, it ufually returns through them to the heart again in an uniform and equable motion ; and thi3 is not only the cafe in the human body, but alfo in other ani- mals, whether they be in health or in ficknefs. One of the inftances in which the contrary has been obferved, and where the Veins have had a pulfation, is a cafe related by Mr, Hom- berg to the Paris Academy. The patient was a lady of about thiity-five years old, afflicted with a grievous afthma, a pain in the head, a continual want of reft, and terrible palpitations of the heart.

On opening her body after death, the heart was found of twice its natural dimenfionsj its cavities very large, and its fides very thin ; and in each trunk of the arteries there was a flefhy polypus fixed to their internal furface. That in the trunk of 5 E the