Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/321

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complex than the original receipt of that author, and the col- lege have therefore retrenched the number of ingredients in them; and as the medicine is always to be powdered tor ute,

' it is now ordered to be kept in the form of powder.

It is thus prefcribed there : take cerufs, five ounces ; fircoco - la, an ounce; gum tragacanth, half an ounce ; make the whole into a fine powder. Pemlcrtm's Lond. Difp. p. V 2 -

Pulvis umtr'ayerv* cactus, the name given in the late Lon- don difpenfatory to the compofition ufually called /«;« antra-

yervee.

The preparation is

alfo there made much lefs complex, by leaving outthelefa powerful abforbent powders, and ufmg the compound powder of crabs claws in the place of all. This is now ordered to be made only of the compound powder of crab's claws, a pound and half; and contrayerva-root, five ounces. Pemberton's Lond. Difp. p-3'3-

Pulvis e myrrba, a form of medicine prefcribed in the late Lon- don difpenfatory, to fupply the place of the troches of myrrh. The compofition is the fame but for the omiffion of one or two of the ingredients, fuppofed not of the fame virtues with the reft, or very difagreeable to the tafte. It is ordered to be made thus : take of dried leaves of rue, of dittany, of crete, of myrrh, each an ounce and half's ol ana fcetida, fagapenum, Ruflia caftor, and opopanax, each an ounce, beat altogether to a fine powder. Pemberton's Lond. Pharm. p. 314.

Pulvis e f common: o, a name given in the late London difpenfa- tory to the purging powder commonly called the Earl of IVar- ivUk's powder.

It is, however, wholly altered here, the cryftals of tartar and diaphoretic antimony being left out, and the medicine ordered to be made only of four ounces of fcammony, and three ounces of burnt hartfhorn reduced together to a fine powder. Pem- he< tons Lond. Di r p. p. 315.

Pulvis e fuccino y amber -pfrwder, a form of medicine prefcribed hi the late London pharm acopcea, to ft and in the place of the troches of amber, or tnch'fd de carabe of former difpenfa- torics. The compofition of the powder is this: take prepared amber

and

gur

arabic, of each ten drachms ;

of hypociftus,

balauftines, and Japan earth, of each five drachms ; olibanum, half an ounce ; {trained opium, a drachm ; mix all together into a fine powder. Pcmberton's Lond. Difp. p. 316.

VvLvisfceamdans-, in natural hiftory, a name given by late writers to that fine powder which is. contained in capfules upon the ftamina or threads in the flowers of plants, and is called by fome Englifh writers the makdujl^ and in general the fa- rina of flowers.

This duft was for many ages looked upon as a recrement of the plant; but it has of later times been found to confitt wholly of or^anical bodies, which are in reality the embryo plants ; and entering into the feeds in the capfules, while yet buried in the ftyle, they fcecundate them, and put them in a ftate to vegetate and produce their fpecies. On the molt accurate ex- amination, however, with microfcopes, the farina, or puhis fcecundam of plants, has never been found to carry any like- nefs to a plantula femtnath^ or the rudiments of the plant which was to be produced by it. All that the microfcope docs in this cafe, is but increafing the apparent magnitude of the par- ticles of the powder; but they are found, when thus viewed, to be no other than a congeries of globules, which are all alike in the fame fpecies, and compofed of fibres and vaficules wrought together in fuch a curious manner, to the keeping whole as long as neceflary, and burfting when necefTary, that It appears evident they are deftined for fome very great ufes. See Tab. of microfc. Obj Clafs 2.

Verdrefius, in the Afla eruditorum, has given a very curious detail, and has figured and defcribed fifty kinds of this duft, moft of which are confiderably different from one another ; tho' fome are nearly alike. He obferves, that in all the num- ber of flowers he examined, he found no farina, or pulvis fecundans, that did not refemble one of thefe fifty ; and that, therefore, whoever engages in this curious refearch, fhouiu f.rft obferve thefe, and then refer the others to one or other of them, as they next approach them, and mention their differences, if any, by way of characters, by which they might always be known. Act. Erudit Ann. 1794. p. 410. The author of this curious treatife, from a multitude of expe- riments, feems to think thefe globules of duft rather to repre- fent the tefticles of male animals, than any other part of the organization of any known body. The numerous fibres they are compofed of, which are convoluted and twifted in a molt remarkable and intricate manner, and the vefides contained in their fubftance among thefe fibres, fhew a great refemblance -to the teftes in ftru&ure, and in their apparent ufes. The principal farinse he defcribes, are thofe of the yellow water iris, or flag-flower, which are of an oyal figure, fome- what hairy, and covered either in part or entirely with a thin membranous coat. The tulip farina, which is flat, broad, and fonvwhat angular at one etui, tho' rounded at the other. The honey -fuckliT farina, which is broad and truncated at one end, find roundifii, but fomewhat pointed at the other. 'The farina cf the iris-leaved yellow lilly, which is oblong, pointed at

- *>ne end, and rounded at the other ; and when feparated per-

P U M

ftdf from its capfule, has a tail at the rounded or largeft ehu. The farina of the hypericum, which is oblong and Mender, truncated at both ends, and marked witii a deep longitudinal furrow on one fide, refenibling the channel in the midft of the feeds of corn or oats, and fetving to the fame purpofej the opening of the granule. The marfhniallow farina, Which is like the mallow and holy oak, a very beautiful object, being round granules, furrounded with a regular circle of fpines of prickles. The Indian crefs has a farina, which in moft lights appears of a triangular figure. T he lyfimachia, or willow- herb, has a farina refcmbling that of the hypericum, but fhotter and thicker, truncated at both ends, and with a longi- tudinal furrow, tho' but a flight one. That of the fcabious is fmoothcr than moft others, and approaches moft of all to a globular figure. That of wormwood is alfo globular, and final), and when feparated entire, has a ftalk or pedicle like that of the yellow lilly. The farina of the clematitis is very fingular, it being of a globular figure, but confifting of one globule enclofing another ; or of a pale-coloured globule, con- tained in a thick brownifh hulk, which opens in one deter- mined part, and lets out the globule it contained. That of the white jeffamine confifts of half globules, or a fort of hc- mifpheres, flat on one fide, and regularly rounded on the other.

The farina of tobacco is oblong and flender, and pointed at both ends, fometimes very fharply, fometimes more obtufely, according to its ftate of ripenefs. This has alfo an oblong furrow running from end to end on one fide, which is the place where it is to open, as the hypericum and fome others have. The farina of the paffion flower confifts of very large dufky-coloured globules, which, when feparated entire, have tails or pedicles ; but thofe very fhort. 1 hat of the gourd is a more elegant object than almoft any other : it is round, and furrounded with a row of flat and obtufe rays, refembling the mallow farina, except that they are not pointed. The cucum- ber, tho' a plant nearly allied to this, yet produces a fimple, fmall, and roundifh farina. The cabbages of fome kinds have farina? compofed. of fimple, oval bodies ; in others thefe globules are more oblong, and refemble very perfectly the naked grains of wheat, having the fame fort of furrow run- ning longitudinally from end to end. The duft of the hya- cinth is very long and flender, often crooked, and always ob- tufe at one end, and pointed at the other. '1 he farina of fome of the fpecies of clary is very large, perfectly round and fmoothj and has the mark of an opening in one part. It is probably- like that of the clematitis, one globule contained within ano- ther, and this the opening thro' which the inner one is to pafs. The author of thefe curious obfervations has given good figures of thefe and of the other of the fifty of his farina:, to which we refer the reader. A3. Erudit. Ann. 1714. p. 4.11.

Ptiteotamts Pulvis, in natural hiftory, the name of a foffile fub- ftance, found in form of powder, and famous for its confoli- dating undrr water. The accounts of it feem, however, to be a little erroneous.

The fubftance itfelf is a pale greyiftl powder, Compofed of particles fo extremely -minute, as to efcape the diftinclion even of the heft glaffes, and appear, when viewed by the microf- cope, only a loofe, very fine, irregular powder. It has among it a few fmall fpangles of talc, and being fhook up in a vial of water, leaves a whitifh muddinefs in it, which is very long in fubfiding. If wetted with falt-water, it immediately dries into a firm folid mafs, like a ftone. It does the fame alfo in common water ; but the mafs is lefs firm. The antients were well acquainted with this fubflance and its properties. It is faid, indeed, that on running down into the water, it becomes a hard ftone, while it remains under it } but this is probably a miftake, arifing from this, that the pow- der was continually running down the hills into the fea, and lodging on their fides in large quantities in many places ; when thefe maffes became wet with the waves, in ftorms or high tides, and afterwards deferted by them, they naturally harden- ed into fo many mafl'es of a fort of ftone : and thefe were pro- bably what authors have feen and defcribed, for they never, probably, fearched for thefe maffes under water. The prin- cipal ufe of this powder among the antients, was in mixing with their cements for buildings funk into the fea. It is at prefent well known in France and Italy, as an ingredient in that fort of plaifter they call po%%olane.

The remarkable quality of its coalefcing on its being mixed with water, is probably owing to its having in its compofition a quantity of a certain earth known in almoft all ages and countries for coalefcing into a kind of plaifter without pre- vious burning. The antients knew this earth by the name of gypfum tyinpbaiam ; and we, by that of calx native. It is very common on the fides of hills in many parts of Italy. Hilts Hift. of Foff. p. 573.

PUMICK (Cycl.)— There have been many different conjectures about the nature and origin of this fubftance ; but the very earliefr. writers of antiquity, and the moft judicious of the later ages, agree, that it is no native foffile, nor in its original condition but a mere cinder, or remainder of fome other foffile body, calcined by a violent fire.

This may have been either fubterranean and unfeen, or per- haps fincc extinguifhed ; or that of the well-known burning