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tion rauft be carefully obferved, according as the congelation of the fait is intended to be haftened or retarded. In the com- mon way of evaporating lixiviums of this kind in earthen veflels over a naked fire, a great quantity of the fait is always loft y part of this is carried off with the vapours raifed too haftily in this manner, and part penetrates the fides and bot- tom of the veffel, though it be ever fo well glazed. The quantity of water necefTary, is, in moft cafes, about five pints to two pound weight of the afhes. After all the fait that can be got is extracted by this operation, the afhes being cal- cined again in a kiln, will afford more fait of the fame kind, but in a much fmaller quantity.
The falts of Vegetables made in this manner, are fubject to run into water in damp weather, unlefs very carefully kept; but in this, art may be employed, and the running in a great meafure prevented. Thus, iffomefulphur be added to the afhes, when their burning is almoft over, and confumed by burning a- mong them, very little difference will be made in the nature of the falts, but they will be more white and ciyftalline, and will keep much better. The proportion of fulphur is to be in fome meafure regulated by the quantity of fait the afhes are known to yield ; but on a medium, five ounces of fulphur is enough to add to a hundred pounds of afhes. When the ve- getable falts are thus made, they have each their peculiar figure, and this they retain, though diflolved and cryftaiized again ever fo often. If two or three of thefe falts, thus care- fully made, and which have each their determinate figure, be diflolved together in water, they will each of them {hoot again feparate, and in their refpectivc figures, not mixing and form ing different figures, as might be expected. This experiment holds good alfo, not only in thefe falts, but in all other kinds, which have naturally their determinate figures : thus, if in a veffel of water, there be diflolved toge- ther fome blue vitriol, fome roach alum, and fome fait petre, the whole liquor will be of a blue colour from the vitriol ; but when it is carefully evaporated to a proper ftandard, the falts wiil all form themfelves again into their own regular and na- tural cryftals : the vitriol will be blue as before, but all the reft, though found in a coloured fluid, will be as colourlefa as at firft, and each will have its own determinate fhape. Though the lixivia! fait of every plant thus treated, have its own peculiar figure, when diflolved, and regulaily (hot again ; yet, as in the fea (alt, and fome other natural falts, there ap- pear, on cryllallization, maffes of different figures, fo in fome of thefe the fame fait will have two or three different figures, all peculiar however to itfelf. Two forts of cryftals have been obferved in the falts of the lettuce, the fcozonera, the melon, and fome others : three forts in the black pepper, and in the flowers of the red rofe j and four forts in the falts of the roots of white hellebore.
Eefides this diverfity of figures in many of the kinds 'of falts, there is one kind of cryftals which run through the falts of al moft all the kinds, in a greater or lefler proportion : thefe are certain cubic grains or cryftals. It is probable, that thefe are cryftals of fea fait, which is a fait found mixed among many others, and is naturally of this cubic figure in its firft or fimple concretions. It feems alfo a general rule, that the different parts of the fame plant form cryftals of a different figure; for the leaves of laurel form cryftals very differently fhaped from thofe procured from the wood of the fame tree ; and the figures of the cryftals in the fait of the pulp of a gourd lire very different from thofe of the falts made from the rind of the fame fruit. See Tab. of Microfcopical Objects, Clafs 3. Many falts made from different fubftances, have either abfo- lately the fame or very fimilar figures in their cryftals. The fait of the cucumber has a figure very like that of the fait of eye-bright ; and the fame form is obferved in the cryftals of orange-flowers, endive, liquorice, and many other plants. In order to obtain thefe feveral cryftals of the lixivial falts, de- terminate and exact in their figures, and not mixing one with another, it is ncceflary to ufe great caution in the evaporating the lye ; for if it be totally evaporated, there remains only a cruft of fait at the bottom of the veflel, if it be only too far evaporated, though not totally : the falts fhoot into large cluf- ters, and are never regular and perfect ; and finally, if the lye is left too weak, then the evaporation afterwards, in order to the forming the cryftals, is fo tedious, that few can have patience to attend to it. Nothing but practice and experience can dictate when to ftop the evaporation; but when this has been learned, the veffel is to be taken out of the balneum ma- ria, and the clear liquor is to be poured out of it into feveral fmall vials. Thefe are to be flopped to keep out duff and moi- fture; and, after a time, the falts will congeal into cryftals, which will be fixed to the fides and bottoms of the 'vials, in their true and proper ftiapes, and in the likenefs of rock-cry- ftal, as to brightnefs and tranfparency.
Different plants and trees yield afhes, which are impregnated in a different degree with falts. The fame plants, at different feafons of the year, contain a!fo different quantities ; and all thefe varieties make it necefTary to attend carefully to the time of (topping the evaporation. It is alfo to be obferved, that there is a great difference in the quantity of afhes, to which plants and their flowers and fruits burn, as well as in that of the fait they yield ; and what is moft remarkable, is, that thefe have no
connection one with the other. There are various inftances of this kind in Redi's paper ; he obferves particularly, that an hundred weight of orange flowers reduced to afhes, yielded only four pounds fix ounces of them, and thefe afhes only five drams of fait : that eight hundred weight of gourds made only- four pounds of afhes ; but thefe yielded no lefs than ten ounces of fait, while an hundred weight of maiden-hair yielded nine pounds of afhes, and thefe only four drams of fait. A great number of other proceffes of this kind are mentioned in the fame place ; to which we refer the curious. It was obferved, that all thefe falts thus cryftallized, had a purging virtue, from whatever plant they were made ; and the fait drawn from pomegranate peels, or other aftringents, is as ftrongly purgative, as that from the moft purgative drugs. The dofe in which thefe falts are to be taken, is from half an ounce to an ounce diflolved in warm water ; and it is all the fame thing what Vegetable they are made from ; the fharp- pointed cryftals and the blunt ones having the fame degree of virtue. Garlick, and the like ftiop Vegetables, yield no fait at all of this kind. Philof. Tranf. N°. 243. p. 296. VEGETATION (Cyr/.)— -The great attention of all who ftudy botany, is at prefent placed on the difcovery of new plants ; but we are yet unacquainted with many peculiarities in the moft common ones, which may prove not a lefs worthy employ- ment for our thoughts.
The irregularities in the Vegetation of the feveral parts of plants feems a fubject well deferving our attention ; and Mr. Marchand has laid before us an inftance of this in one of our moft vulgar plants, the common garden radifli. In the month of July, this gentleman obferved a plant of this fpecies, which had accidentally fixed itfelf in an open place, and was then full of flowers and pods. Toward the end of one of the branches, he obferved a kind of tuberofity of an oblong fhape, which looked fomewhat like one of the pods of the plant, but that it was too long, and was very oddly twill- ed and contorted ; this daily increafed in fize, and in a week was come to its full growth, which was, in the whole, about two inches and a half in length, and three quarters of an inch thick. It was of a very rough and knotty furface, and like the reft of the ftalk, had feveral pedicles of flowers growing on each fide from it ; it terminated in a fmooth end, divided in- to three parts, which all turned upwards. The longeft of thefe points terminated in a green cartilaginous flower of the fame fubftance with the protuberance which pro- duced it ; in this there were all the regular parts of the flowers of the more perfect kind ; there were four leaves which ferved for a cup ; four more within thefe, which reprefented the petals; fix other fmall bodies there flood in the middle of the flower, which reprefented the ftamina ; and among thefe another body which reprefented the piftil; fothat, here was in this irregular Vegetation, a reprefentation at large of every part of the perfect flower of the radifh, excepting only the apices ; but thefe were all very different in their nature and ftruiturc, from their fimilar parts in the natural flowers, be- ing all of a hard, thick, and tough cartilaginous fubftance, and in colour of a greenifh brown.
The fhortfcft of the three points which terminated this tube- rofity, had alfo at its end a refemblance of a flower compofed of all the parts mentioned in the former, and of the fame co- lour and fubftance with it, only differing in being a little fmaller : and the third point had no regular refemblance of a flower, but was of the fame cartilaginous fubftance, and of a femi- circular figure, and had its upper furface ornamented with feveral irregular protuberances. This irregular Vegeta- tion remained in vigour till October, when it gradually faded away, and there was no appearance of feeds in any part of it. The radifh, when its ftalks are wounded by the pucerons, or other infects, will often throw out a protuberance of fome ir- regular figure ; but the refemblance of flowers in this, was a angularity never before obferved.
To explain this, it will be necefTary to obferve, that every or- ganized part of a plant contains in it a number of invifible fe- mlnal principles, capable of producing plants like that to which they have owed their origin ; and this is a truth of which the fucceeding inftances will all bring very familiar and obvious proofs.
The graft of a tree, which from only one Tingle bud, produces a tree like that from which it was taken, certainly acts upon this principle; for the whole tree is quite different from the flock on which it is grafted, which ferves for no other pur- pofe but merely to convey to it a proper nutritive juice for the developing its parts.
We very well know, that there are many roots, which being cut into little flices of only a quarter of an inch thick, each of thefe will propagate its fpecies, and fend up new plants, like that which the root belonged to ; and fome roots being fplit longitudinally into four quarters, each of thefe will in die fame manner grow and flouiifh, and fhoot out roots from one part, and ftalks from another, fo as to furnifh perfect plants the fame year : and how can this be, but by their having been feminal points in all thefe pieces and fections of roots, which being di- lated, and put in action by the humidity of the earth, have grown into perfect plants. Several of the bulbous rooted plants pro- duce off-fets from the feveral fcales of their roots, andfiom-the 2 * ■ Tides
