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THE

LONDON ENCYCLOPÆDIA,

OR

UNIVERSAL DICTIONARY

OF

SCIENCE, ART, LITERATURE, AND PRACTICAL MECHANICS,

COMPRISING A

POPULA) VIEW OF THE PRESENT STATE OF KNOWLEDGE.

ILLUSTRATED BY

IJMEROUS ENGRAVINGS, A GENERAL ATLAS,

AND APPROPRIATE DIAGRAMS.

Sic oportet ad librullresertim miscellanei generis, legendum accedere lectorem, ut solet ad conviviuni conviva civilis.
Coprivator annititur opiniisatisfacere; et tamen si quid apponitur, quod hujus aut illius palato non respondeat, et hic et ille
urbane dissimolant, et alia yıla probant, ne quid contristeniconvivatorem.

Erasmus.
A reader should sit dot a book, especially of the miscellaneous kind, as a well-behaved visitor does to a banquel. The
Erster of the least exerts hijf to satisfy his guests; but if, after all his care and pains, something should appear on the table
that does not suit this or that son's taste, they politely pass it over without notice, and commend other dishes, that they may not
dutress a kind bool.

Translation.

BY THE ORIGINALDITOR OF THE ENCYCLOPÆDIA METROPOLITANA,

ASSIST BY EMINENT PROFESSIONAL AND OTHER GENTLEMEN.

IN TWENTY-TWO VOLUMES.

VOL. XVIII.

LONDON:

PRINTED į THOMAS TEGG, 73, CHEAPSIDE;
SOLD BY N. HAILES, PICCADILI E. WILSON, ROYAL EXCHANGE ; J. MASON, CITY ROAD;

BOWD & KERBY, OXFORD STREET:
GRIFFIN & CO. GLASGOW: J. CUNG, DUBLIN: M. BAUDRY, PARIS : F. PLEISCHER, LEIPSIC:
AND WHIPPI LAWRENCE, SALEM, NORTH AMERICA.

1829.

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11-7-52

THE

LONDON ENCYCLOPÆDIA.

11-17 52 MELO

POT, n. s.
Fr. and Belg. pot, in all Let me see her Arabian pothooks..

Id. PO'TABLE, adj. the senses; Islandic and

The sheep went first to pot, the goats next, and Pota'tion, n. s. Dan. potte ; Goth. pott. A after them the oxen, and all little enough to keep POT'HERE, vessel in which meat is

Jife together.

L'Estrange. Рот'ноок, ,

boiled;
; any vessel to hold

Whenever potters meet with any chalk or marl

mixed with their clay, though it will with the clay POT’LID, liquids; a cup: to go to

hold burning, yet, whenever any water comes near POT'SHERD, pot,' to be destroyed or

any such pots after they are burnt, both the chalk Por’TAGE,

devoured : to pot is to pre- and marl will slack and spoil their ware. POT'TER. serve in pots : potable is

Mortimer, drinkable : potation, a draught : potherb is a Acorns, mast, and other seeds may be kept well, herb fit for boiling: pot-hook and pot-lid ex. by being barrelled or potted up with moist sand. plain themselves : potsherd (pot and sherd, from

Id. Belg. schaerde ; properly potshard), a fragment of A potter will not have any chalk or marl mixed a broken pot : pottage, any thing boiled for food. with the clay.

Id. Husbandry.

Pot them in natural, not forced earth ; a layer of Jacob sod pottage, and Esau came from the fie.a

rica mould beneath and about this natural earth to faint.

Genesis.

nourish the fbres, but not so as to touch the bulbs. The woman left her water-pot, and went her way. John.

Evelyn.

Where solar beams He on the ashes sits, his fate deplores ;

Parch thirsty human veins, the damasked meads And with a potsherd scrapes the swelling sores.

Sandys.

Unforced display ten thousand painted flowers
Useful in potables.

Philips.
Toad that under the cold stone
Sweltered, venom sleeping got ;

Sir Tristram telling us tobacco was a potherb, bid

the drawer bring in t' other half pint. Tatler. Boil thou first i' th' charmed pot. Shakspeare.

Suppose your eyes sent equal rays But that I think his father loves him not,

Upon two distant pots of ale, I'd have him poisoned with a pot of ale. Id.

Not knowing which was mild or stale. Prior. My thoughts are whirled like a potter's wheel.

Id.

He like the potter in a mould has cast
The world's great fame.

Id. I learnt it in England, where they are most potent

John's ready money went into the lawyers' pockets ; in potting.

Id. Othello.

then John began to borrow money upon the bank Thou best of gold art worst of gold,

stock, now and then a farm went to pot. Other less fine in carat is more precious,

Arbuthnot's History of John Bull. Preserving life in medicine potable. Shakspeare.

Of alimentary leaves, the olera or potherbs afford If I had a thousand sons, the first human princi

an excellent nourishment; amongst those are the ple I would teach them, should be to forswear thin

cole or cabbage kind.

Arbuthnot. potations, and to addict themselves to sack.

The columella is a fine, thin, light, bony tube, the Id. Henry IV.

bottom of which spreads about, and gives it the reAt this day at Gaza, they couch potsherds of vessels of earth in their walls to gather the wind from semblance of a wooden potlid in country houses.

Derham. the top, and pass it in spouts into rooms.

A soldier drinks his pot, and then offers payment. Bacon's Natural History.

Swift. Dig a pit upon the sea shore, somewhat above the

Leaves eaten raw are termed sallad ; if boiled, high-water mark; and sink it as deep as the low; they become potherbs : and some of those plants water mark; and, as the tide cometh in, it will fill which are pot-herbs in one family, are sallads in anwith water fresh and potable.

Bucon.
other.

Iatts. The said potable gold should be endued with a capacity of being agglutinated and assimilated to the who seasons

pottage, or expels the gout;

For great the man, and useful, without doubt, innate heat.

Harrey.

Whose science keeps life in, and keeps death out. Rivers run potable gold. Milton's Paradise Lost.

Harte. Gigantic minds, as soon as work was done, To their huge pots of boiling pulse would run,

POT'AGER, n. s. From Pottage. A porFell to with eager joy.

Dryden.

ringer. Potted fowl and fish come in so fast,

An Indian dish or potager, made of the bark of That ere the first is out the second stinks, a tree, with the sides and rim sewed together after And mouldy mother gathers on the brinks. Id. the manner of twiggen-work. Grew's Museum. Whence come broken potsherds tumbling down, POTAMOGETON, pond weed, a genus of And leaky ware from garret windows thrown: Well may they break our heads.

Id.

the tetragynia order, and tetrandria class of plants; Some press the plants with sherds of potter's clay. natural order fifteenth, inundatæ : cal. none;

Id. petals four; no style, and four seeds. There Egypt baser than the beasts they worship;

are twelve species, all of them vegetables floating Below their potherb gods that grow in gardens.

on the surface of stagnant waters, affording

Id. agreeable shade to fish, and food to cattle.
Vol. XVIII.-PART 1.

B

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A West Elm

POTAMON, or Potamo, a philosopher of so small that no person could be remunerated by Alexandria. He attached himself to none of the it for the trouble of the process.

Messrs. Tayschools of philosophy of his time; but kept a lors of Queensferry, by desire of Sir John Hay, middle course between the scepticism of the made an experiment on the produce of two acres Pyrrhonians and the presumption of the dog- of potato stalks, which yielded two casks of matists. He was the first projector of the Eclec- ashes, weighing 2 cwt. 23 lbs., which produced tic sect; for, though their mode of philosophising of soluble substance only 36 lbs., containing a had been common before, he was the first that great deal of muriate of potash and sulphate of attempted to institute a new sect on this prin- potash. The value of this produce was not ciple.” Diogenes Laertius relates that, not long more than 2d. per lb., or 6s. in all; and on before he wrote his Lives of the Philosophers, twelve acres of their own they had a similar an Eclectic sect, εκλεκτικά τις αιρεσις, had been result. introduced by Potamo of Alexandria, who se The following is a table of the saline product lected tenets from every former sect. Suidas of 1000 lbs. of ashes of the following vegetables :and Porphyry also mention him. The time

Saline products. when Potamo flourished is uncertain. Suidas Stalks of Turkey wheat, places him under Augustus: but it is more pro

198 lbs.

or maize, bable, from the account of Laertius, that he flou- Stalks of sunflower 349 rished about the close of the second century.'

Vine branches

162.6 POTAR'GO, n. s. Ital. potarge.

166 Indian pickle.

Box

78 What lord of old would bid his cook prepare Sallow

102 Mangos, potargo, champignons, cavarre ?

King.
Oak

111 POT'ASH, n. S. Fr. potusse. The vegetable Aspen

61 alkali. See below.

Beech

219 Cheshire rock-salt, with a little nitre, allum, and Fir

132
potash, is the flux used for the running of the plate-
glass.

Sor 125 according
Woodward.
Fern cut in August 116

I to Wildenheim. Potash, or Potassa, in chemistry and the Wormwood

748 manufactures, more commonly known as the vege- Fumitory

360 table alkali, is a fixed alkaline salt obtained from Heath

115 Wildenheim. the ashes of burnt vegetables of various kinds. The method of making potash is described by On these tables Kirwan makes the following Dr. Shaw as follows:-Burn a quantity of billet remarks:-1. That in general weeds yield more wood to gray ashes; and, taking several pounds ashes, and their ashes much more salt, than of these ashes, boil them in water, so as to make woods; and that consequently, as to salts of the a very strong lixivium or lie. Let this lie be vegetable alkali kind, as potash, pearl-ash, cashup, strained through a coarse linen cloth, to keep out &c., neither America, Trieste, nor the northern any parts of half-burnt wood that might happen countries, have any advantage over Ireland. 2. to remain in the ashes; then evaporate this That of all weeds fumitory produces most salt, and strained lie in an iron pan, over a quick fire, next to it wormwood. But, if we attend only to almost to dryness: then, taking out the matter the quantity of salt in a given weight of ashes, remaining at the bottom, and putting it into an the ashes of wormwood contain most. Trifolium iron crucible, set it in a strong fire till the matter fibrinum also produces more ashes and salt than is melted, and then immediately pour it out fern. Dr. John of Berlin observes that uncomupon an iron plate, where it soon cools, and ap- bined potash does not occur in living vegetables, pears in the form of a solid lump of potash. În it being always combined with an acid, and is this manner potash is made in the large way of only found in them when they are in a state of business, for the service of the soap-boiler, glass- putridity or decomposition. Plants that feel maker, fuller, &c.; but, according to the differ- rough and sharp, particularly equiseti, contain ence of the wood, or combustible matter em- much siliceous earth; in the latter full thirteen ployed, with the manner of turning it, and per cent. Lichens that grow on the summits of conducting the process, different kinds of potash fir trees contain an uncommon proportion of are prepared. There are certain saline plants oxide of iron, which, Dr. John remarks, may be that yield this potash to great advantage, as par- viewed as illustrative of the formation of iron by ticularly the plant kali; there are others that af- the vegetable process. Dr. John recommends ford it in less plenty, and of an inferior quality, the use of decaying and diseased wood to those as bean-stalks, &c.; but, in general, all vegetable who wish to obtain potash from it by burning, subjects afford it of one kind or other, and may as he maintains that the quantity of potash is most of them be made to yield it tolerably per- much increased by the putrefactive process. fect after the manner of the process already laid This remark is not new; for we find it mentioned down, even the loppings, roots, and refuse parts in the second volume of Schreber's Sammlung of ordinary trees, vine-clippings, &c.

verschiedener Schriften, published in 1763, that It was announced in the philosophical Jour- putrid wood was recommended for obtaining nals that, in France, potash had been obtained ashes in preference to fresh wood. Plants, in great quantities from potato stalks. In order which were allowed to grow in a solution of to put this to the test of experiment, Sir John natron, absorbed by their roots a considerable Hay and Dr. M'Culloch made a trial on a large portion of the alkali; but none of this appeared scale, and found that the quantity of potash was when the ashes of the plant were examined: in

place of it appeared potash; and hence it is con- part of the body, it destroys it almost instanjectured that vegetables have the power of con- taneously. On account of this property it has verting natron into potash.

been called caustic, and is often used by surThe process for obtaining pot and pearl-ash is geons to open abscesses, and destroy useless or given by Kirwan as follows : -

hurtful excrements. When heated it melts. At 1. The weeds should be cut just before they a red heat it swells, and evaporates slowly in a seed, then spread, well dried, and gathered clean. white acrid smoke. When exposed to the air it

2. They should be burned within doors on a soon attracts moisture, and is converted into a grate, and the ashes laid in a chest as fast as they liquid ; and combines with carbonic acid, for are produced. If any charcoal be visible, it which it has a great affinity. It has a very should be picked out, and thrown back into the strong affinity for water. At the common temfire. If the weeds be moist, much coal will be perature of the air, one part of water dissolves found. A close smothered fire, which has been two parts of potassa. The solution is transparecommended by some, is very prejudicial. rent, very dense, and almost of the consistence

3. They should be lixiviated with twelve.times of oil. In this state it is usually employed by their weight of boiling water. A drop of the 'so- chemists. When four parts of potash in powder, lution of corrosive sublimate will immediately and one of snow are mixed together, the mixture discover when the water ceases to take up any becomes liquid, and absorbs a quantity of camore alkali. The earthy matter that remains is loric. This mixture was employed by Lowitz to said to be a good manure for clayey soils. produce artificial cold. When the aqueous so

4. The lie thus formed should be evaporated lution of potash is evaporated to a proper conto dryness in iron pans. Two or three at least sistency, the potash crystallises. The shape of of these should be used, and the lie, as fast as it its crystals is very different, according to the is concreted, passed from the one to the other. way in which they have been produced. When Thus, much time is saved, as weak lies evapo- allowed to form in the cold, they are octahedrons rate more quickly than the stronger. The salt in groups, and contain 0:43 of water: when thus produced is of a dark color, and contains formed by evaporation on the fire, they assume much extractive matter; and, being formed in the figure of very thin transparent blades of exiron pots, is called potash.

traordinary magnitude, which, by an assemblage 5. This salt should then be carried to a rever- of lines crossing each other in prodigious numberatory furnace, in which the extractive matter bers, present an aggregate of cells or cavities, is burnt off, and much of the water dissipated : commonly so very close that the vessel may be hence it generally loses from ten to fifteen per inverted without losing one drop of the liquid cent. of its weight. Particular care should be it contains. Potash is not altered by exposure taken to prevent its melting, as the extractive to the light. matter would not then be perfectly consumed, A perfectly pure solution of potash will reand the alkali would form such a union with the main transparent on the addition of lime-water, earthy parts as could not easily be dissolved. show no effervescence with dilute sulphuric acid, Kirwan adds this caution, because Dr. Lewis and not give any precipitate on blowing air and Mr. Dossie have inadvertently directed the from the lungs through it by means of a tube. contrary. This salt, thus refined, is called pearl Pure potash for experimental purposes may ash, and must be the same as the Dantzic pearl-ash, most easily be obtained by igniting cream of

To obtain this alkali pure, Berthollet recom tartar in a crucible, dissolving the residue in mends to evaporate a solution of potash, made water, filtering, boiling with a quantity of quickcaustic by boiling with quicklime, till it becomes lime, and, after subsidence, decanting the clear of a thickish consistence; to add about an equal liquid, and evaporating in a loosely covered silWeight of alcohol, and let the mixture stand some ver.capsule, till it flows like oil, and then pourtime in a close vessel. Some solid matter, partlying it out on a clean iron plate. A solid white crystallised, will collect at the bottom; above cake of pure hydrate of potash is thus obtained, this will be a small quantity of a dark-colored without the agency of alcohol. It must be imfluid; and on the top another lighter. The latter, mediately broken into fragments, and kept in a separated by decantation, is to be evaporated well-stoppered phial. quickly in a silver basin in a sand-heat. Glass, As 100 parts of subcarbonate of potash are or almost any other metal, would be corroded by equivalent to about seventy of pure concentrated the potash. Before the evaporation has been oil of vitriol, if into a measure tube, graduated carried far, the solution is to be removed from into 100 equal parts, we introduce the seventy the fire, and suffered to stand at rest; when it grains of acid, and fill up the remaining space will again separate into two Auids. The lighter, with water, then we have an alkalimeter for estibeing poured off, is again to be evaporated with mating the value of commercial pearl-ashes, a quick heat; and, on standing a day or two in which, if pure, will require for 100 grains 100 a close vessel, it will deposit transparent crystals divisions of the liquid" to neutralise them. If of pure potash. If the liquor be evaporated to they contain only sixty per cent. of genuine suba pellicle, the potash will concrete without regu- carbonate, then 100 grains will require only sixty lar crystallisation. In both cases a high-colored divisions, and so on. When the alkalimeter inliquor is separated, which is to be poured off; dications are required in pure or absolute potash, and the potash must be kept carefully secluded such as constitutes the basis of nitre, then we from air

must use 102 grains of pure oil of vitriol, along Its taste is remarkably acrid, and it is so ex- with the requisite bulk of water to fill up the ceedingly corrosive that, when applied to any volume of the graduated tube.

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