Chapter C: W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the (24)

=BANE.= Poison; anything deleterious or destructive; a word often found joined to another, in the popular and vulgar names of plants and disease, to denote their character; as BANE'-BERRY, the herb Christopher; BANE'-WORT, deadly-nightshade; SHEEP'S BANE, the rot; &c.

=BANG, Bangue= (b[)a]ng'). [Nat.] See HEMP, INDIAN.

=BAN'IAN= (b[)a]n'-y[)a]n). The _fi'cus In'dicus_ (Linn.), or Indian fig. The fruit and young branches yield one species of gum-lac; and both the juice and bark are used medicinally.

Among sailors, BANIAN' DAYS are those on which butcher's meat is not served up at dinner.

=BANN'OCK= (-[)u]k). In Scotland and the northern counties of England, a flat round cake made of oat, rye, or barley meal, baked on an iron plate over the fire, or on the hot hearth.

=BARBS.= _Syn._ LAMPAS, SKEW. This occurs in horses from two to four years old, and arises from a little inflammation of the ridges that pass along the palate, above and behind the incisor teeth, occasionally preventing the animal from eating and setting up slight fever. The best treatment is to scarify the enlarged ridges freely with a lancet or penknife, and to give for a time bran mashes, soaked grain, and other soft food.

=BAR'BERRY.= _Syn._ PEP'PERIDGE-BUSH[double-dagger], THORNY BOX'-TREE*; BER'BERIS, B. VULGA''RIS (Linn.), L.; EPINE-VINETTE, VINETTIER, Fr.; BERBERITZE, Ger. A perennial bush or shrub common in woods and hedges. Berries (BAR'BERRIES, PEP'PERIDGES), gratefully acid, cooling, and astringent; used in pastry, but require, according to their degree of ripeness, from one half their weight to an equal weight of sugar. Both bark and berries were formerly esteemed in jaundice, biliary flukes, &c. The crushed berries with water form a refreshing fever-drink. The root dyes a fugitive yellow. See BERBERINE, JAMS, PRESERVES, &c.

=BAREGE= (barège, b[)a]r-r[=a]zhe'). [Fr.] A light woollen fabric so named from having been first made in the valley of Barèges. Of late years Paris has become celebrated for its barèges; but these are generally woven with the 'warp' of silk, and the 'woof' of wool. In the common imitations of the shops, the 'warp' is generally of cotton.

=BAREGINE= (barégine). See GLAIRINE.

=BARIL'LA.= [Eng., Ger., L., Sp.] _Syn._ SO'DÆ CAR'BONAS VENA'LE, L.; BARIG''LIA, BARIL'LOR, Sp., Lev.; BARILLE, SOUDE, Fr. The alkaline residuum of the combustion of salsola, salicornia, chenopodium, and other species of the order Chenopodiaceæ. These plants, which are cultivated on the sea-coast for the purpose, are cut down when ripe, dried, and burned in heaps, on iron bars laid across pits dug in the earth. The alkali and saline matter contained in them is thus fused, and flows into the cavity below, forming, when cold, a hard grey or bluish porous mass which is BARILLA.

_Comp._ Carbonate, sulphate, chloride, and sulphide of sodium, carbonate and sulphate of calcium, alumina, silica, oxide of iron, and imperfectly consumed carbonaceous matter, with a little iodine and bromine. The proportion of soda varies in different varieties:--

ALICANT' BARILLA; obtained chiefly from several species of _salso'la_ and from _chenopo'dium setig'erum_ (-t[)i]j'-), &c.; contains from 25% to 40% of carbonate of soda. (Guibourt.)

CANA''RY B.; from _salso'la ka'li_. (Loudon.) _French barillas_:--

_a._ NARBONNE' B., SALICOR; from _salicor'nia ann'ua_ or _herba'cea_; contains 14% to 15% of carbonate of soda.

_b._ B. OF AIGUEMORTES, BLANQUETTE; from mixed plants; contains 3% to 8% of carbonate of soda. (Guibourt.)

_c._ NOR'MANDY B., N. SODA; from _fuci_.

SIC'ILY BARILLA (s[)i]s'-). Principally from _salso'la sati'va_; furnishes 55% of carbonate of soda. (Fée.)

Good barilla, on the average, contains about 20% of real or available alkali, chiefly under the form of carbonate, besides sulphates, muriates, &c.

_Assay._ See ALKALIMETRY.

_Uses, &c._ Barilla is chiefly used in the manufacture of soap and glass; but the gross quantity imported, though annually increasing, only reached 54,608 _cwt._ in 1856; whilst the exports of soda in the same year reached to about 1,500,000 _cwt._, and in 1859 to above 2,000,000 _cwt._ This enormous quantity was chiefly furnished by our home manufactories.

Barilla is chiefly imported from Spain, Sicily, Teneriffe, and the Levant; but since the introduction of Le Blanc's process for obtaining soda from common salt, its importance and value has considerably lessened. See KELP, SODA, &c.

=BARIUM.= Ba. A metallic radical or element, of which baryta is the chief oxide, and somewhat extensively distributed. First obtained in 1808 by Sir H. Davy. Prepared from baryta by strongly heating it in an iron tube, through which the vapour of potassium is conveyed; the reduced barium being subsequently extracted from the mixed residuum by quicksilver, which is afterwards driven off in a small green-glass retort, in a vapour of mineral naphtha.

_Prop., &c._ Greyish-white, approaching silver in colour and lustre; decomposes water, and gradually oxidises in the air, with the formation of the ordinary oxide (BARYTA). It is malleable, fusible under a red heat; burns in contact with air with a deep red light, and has the sp. gr. 4·70.

_Salts._ Barium forms numerous salts, which are all either colourless or white, except a few, whose acids are coloured, as the chromate, manganate, &c. Some of them are soluble in water; one or two only are soluble in alcohol, and that very sparingly; and (with the exception of the sulphate) they are all extremely poisonous. They may be prepared by saturating solutions of the acids with either baryta-water, or carbonate of barium; and some of them may be prepared by double decomposition.

The various soluble barium salts are known by the following reactions, and they are all (except the sulphate) soluble either in water or in dilute hydrochloric acid, except the nitrate and chloride, which are not soluble in aqueous solutions of their respective acids. Their solutions give an immediate heavy white precipitate with dilute sulphuric acid, and with solutions of the sulphates, which is insoluble in dilute acids and solutions of the alkalies and of the salts of ammonia, that with a solution of sulphate of lime being very sensitive, and characteristic:--Hydrofluosilicic acid gives a very characteristic colourless crystalline and quickly subsiding precipitate, only slightly soluble in hydrochloric acid and nitric acid; alcohol, in equal volume, being added, so hastens and completes the reaction, that the filtrate is unaffected by sulphuric acid:--Chromate of potassium gives a bright yellow precipitate in neutral solutions, soluble in hydrochloric acid and in nitric acid, but insoluble in acetic acid:--Caustic potassa or soda (when quite free from carbonate), and caustic ammonia, cause no precipitate, except in highly concentrated solutions:--Alkaline carbonates give a heavy white precipitate with baryta-water or a solution of baryta, and which is all but insoluble in water, and freely soluble in dilute hydrochloric acid:--Heated with proof spirit, or pyroxilic spirit, the barium salts give a greenish-yellow tinge to the flame:--The barium salts, and particularly the chloride, when exposed on a platinum wire to the inner flame of the blowpipe, colour the outer flame yellowish-green:--Insoluble sulphate of barium may be mixed with powdered charcoal, and exposed for a short time to a full red heat, when sulphide of barium will be formed, which is freely soluble in water, and which, after being neutralised with hydrochloric acid, or acetic acid, will yield a solution suitable to the application of the usual tests. The carbonate, and the salts of barium with the organic acids, are all convertible into pure baryta by exposure to a bright red heat.

Baryta is distinguished from lime and from magnesia by its great solubility in hot water, and by the entire insolubility of its sulphate; from strontia, by being precipitated by hydrofluosilicic acid, and by not giving a red colour to the flame of alcohol; from alumina, by its causticity and alkaline reaction, and by not being precipitated from its solution in water by ammonium sulphydrate.

_Pois., &c._ The sulphate, owing to its insolubility, is the only salt of barium which is not poisonous.--_Symp._ Nausea, vomiting, pains in the head, ringing in the ears, vertigo, and intermitting cramps and convulsions; the respiration is frequently suspended for several moments, and the pupil is generally dilated. The symptoms, however, often vary, and are not very distinctive.--_Treatm., Ant., &c._ Vomiting, followed by copious draughts of water soured with sulphuric acid, or sulphate of soda (Glauber-salt) or sulphate of magnesia (Epsom-salt), dissolved in a large quantity of water. When carbonate of barium has been swallowed, a mixture of one of the above sulphates and weak vinegar should be taken after the vomiting, in order that a soluble barium salt may be first formed, on which the alkaline sulphate will act more readily. Subsequent irritation may be soothed by opium or morphia, and antiphlogistics.

=Barium, Ac'etate of.= Ba(C_{2}H_{3}O_{2}). _Syn._ BARY'TÆ ACE'TAS, L. _Prep._ From dilute sulphuric acid, neutralised with carbonate of barium, and the solution evaporated and crystallised. Very soluble in water; insoluble, or nearly so, in rectified spirit.--_Uses, Dose, &c._ Same as the chloride. It is seldom employed.

=Barium, Arse''niate of.= Ba_{3}(PO_{4})_{2}. _Syn._ BARY'TÆ ARSE''NIAS, L. _Prep._ A solution of chloride of barium is added to another of arseniate of potassium or sodium, and the precipitate collected, washed, and dried. By dissolving this salt in a solution of arsenic acid, and crystallising, BINARSE''NIATE OF BARIUM is obtained. Has been recommended in certain skin diseases, and in phthisis complicated with scrofula.--_Dose_, 1/16 to 1/4 gr.

=Barium, Ar'senite of.= Ba(AsO_{2})_{2}. _Syn._ BARY'TÆ AR'SENIS, L. Very slightly soluble.--_Use, &c._ As the last.

=Barium, Bromide of.= BaBr_{2}. _Syn._ BA''RII BROMI'DUM, L.; BROMURE DE BARYUM, &c., Fr. _Prep._ Boil a solution of protobromide of iron with moist carbonate of barium, in slight excess; filter, evaporate to dryness, and heat the residuum to redness. By careful evaporation of its aqueous solution it may be obtained in crystals. It is soluble in both alcohol and water, and its physiological properties resemble those of iodide of barium.

=Barium, Carbonate of.= BaCO_{3}. _Syn._ CARBONATE OF BARY'TA; BARY'TÆ CAR'BONAS, L.; CARBONATE DE BARYTE, &c., Fr.; KOHLENSAURES, BARYT, &c., Ger. A heavy white mass or powder, very nearly insoluble in water, and decomposed by nearly all the acids. It is found in the crude state abundantly in nature, but can only be obtained absolutely pure by adding an alkaline carbonate to a solution of chloride of barium, or by saturating the hydrate with carbonic anhydride, and in either case washing and drying the precipitate. Native carbonate of barium (_witherite_) is ordered in the pharmacop[oe]ias, and is sufficiently pure for making the barium salts, the only purpose to which it is therein applied.

_Uses._ In _pharmacy_, &c., chiefly to prepare barium salts. In _chemistry_, to separate certain metallic oxides when occurring together in solutions. In the _arts_, as a base for certain delicate colours, as an ingredient in plate-glass, in the manufacture of beet sugar, &c. It is not used in medicine. It is extremely poisonous.

=Barium, Bisulphide.= This substance may be obtained as a fine yellow-coloured product by shaking a solution of barium chloride with a mixture of ammonium sulphide and carbon disulphide. It is insoluble in alcohol, soluble in water, and rapidly dissolved by slightly acidulated water.

=Barium, Chloride of.= BaCl_{2}.2Aq. _Syn._ CHLORIDE OF BARIUM; BARII CHLORIDUM, L.; CHLORURE DE BARYUM, CHLORHYDRATE DE BARYTE, &c., Fr.; SALZSÄURE SCHWERERDE, CHLORBARIUM, Ger. Neutralise a hot dilute solution of hydrochloric acid with carbonate of barium, evaporate down, and crystallise. Sulphide of barium can be substituted for the carbonate. If required chemically pure, gaseous hydrochloric acid is transmitted through a concentrated solution of common or impure chloride of barium, as long as a precipitate forms; the resulting crystalline powder, which is nearly the whole of the chloride of barium present, is collected on a filter, and, after draining, is washed repeatedly with small quantities of pure hydrochloric acid, until the washings, diluted with water, and precipitated with sulphuric acid, give a filtrate which, upon evaporation in a platinum capsule or a watch-glass, leaves no residue; the last traces of acid having been removed by a little alcohol applied in a like manner, the powder is at once dried, and then carefully preserved from the air.--Used in analysis.

_Prop., &c._ Crystals, flat, four-sided tables, colourless and transparent; sometimes double eight-sided pyramids; slightly efflorescent in dry warm air, but otherwise permanent; decrepitate when heated, and lose their water of crystallisation; fuse at a red heat; volatilise at a white heat; insoluble in hydrochloric acid and in alcohol, slightly soluble in rectified spirit, and very soluble in water; water at 60° dissolves 43-1/2% of the crystals, and nearly 37% of the dry salt; and when boiling 75% of the former, and about 66% of the latter; a saturated boiling solution (223° Fahr.) contains 100 parts of water, and 78 parts of the crystallised salt.

The crystals contain 2 atoms of water; and a formula of BaCl_{2} + 2Aq.

_Uses, Phys. eff., &c._ In _chemistry_, it is employed as a test for sulphuric acid and the soluble sulphates. In _medicine_, it has been employed, both internally and externally, as an alterative, resolvent, and deobstruent, in scrofula, glandular swellings, and enlargements, scirrhous cancer, skin diseases, &c.; and more particularly in the first with marked benefit. In large doses it is poisonous. According to Sir B. Brodie, its action on animals is analogous to that of arsenic. Locally, it acts as an irritant. A very weak solution, used as a lotion, often proves serviceable in herpetic eruptions, and as a collyrium in scrofulous ophthalmia. _Dose_, 1/2 gr. thrice a day, in water, gradually increased to 2 or 3 gr.

=Barium, Chlorate of.= Ba(ClO_{3})_{2}. _Syn._ CHLORATE OF BARY'TA; BARY'TÆ CHLO''RAS, L. _Prep._ From a solution of chloric acid neutralised with freshly precipitated carbonate of barium; the resulting solution, after filtration, being crystallised by evaporation.

By passing chlorine through strong milk of hydrate or of carbonate of barium, in the same way as in making chlorate of potassium.

_Prop., &c._ Soluble in 4 parts of cold water. Used in pyrotechny, and to make chloric acid.

=Barium, Ferrocy'anide of.= Ba_{2}FeC_{6}N_{6}. _Syn._ BA''RII FERROCYANI'DUM, L. From pure ferrocyanide of iron digested in baryta water. By careful evaporation, efflorescent prismatic crystals may be obtained, soluble in 4-1/2 parts of water.

=Barium, Fluoride of.= BaF_{2}. _Syn._ BA''RII FLUORI'DUM, &c., L. A white powder, formed by digesting freshly precipitated carbonate of barium in hydrofluoric acid, in excess.

=Barium, Hydrate of.= Ba(HO)_{2}. _Syn._ HYDRATE OF BARYTA; BARYTÆ HYDRAS, L. _Prep._ By digesting caustic baryta, or barium oxide, with a little water, or igniting gently the crystallised hydrate. It can be obtained crystallised as follows:

1. From a concentrated solution of either nitrate or chloride of barium, precipitated with a rather strong solution of pure potassa, or of pure soda, perfectly free from carbonic acid.

2. A strong solution of sulphide of barium is boiled with successive portions of black oxide of copper, until it ceases to give a black precipitate with a salt of lead; the liquid, after filtration, yields crystals of the hydrate on cooling.

=Prop., Uses, &c.= Forms a bulky white powder, containing 10-1/2% of water of hydration, which it retains even after ignition. In this state it is soluble in 20 parts of cold water, and in 2 parts of boiling water. The hot saturated solution, as it cools, deposits abundantly columnar crystals (CRYS'TALLISED HYDRATE OF B.), which contain 51-1/2% of water, of which they lose, by drying and ignition, 88-3/4% (= 4-3/4% of their weight), being reduced to the state of the common or amorphous hydrate. Of all the bases it has the strongest affinity for both sulphuric and carbonic acid, and hence its solution (BARY'TA-WATER) and those of its neutral salts (nitrate or chloride) form our most sensitive tests for these substances. Sp. gr. 4·3 to 4·7. The crystallised hydrate is converted into the ordinary hydrate at a gentle heat, and this last fuses at a low red heat without losing its water of hydration, which it only slowly and with difficulty begins to part with at higher temperatures. In _chemistry_, its uses are, for the most part, similar to those of BARIUM, OXIDE OF.

=Barium, Iodide of.= Ba_{2}I. _Syn._ BA''RII IODI'DUM, L.; IODURE DE BARYUM, &c., Fr.

_Prep._ 1. Dissolve sulphide of barium in water, and add iodine (gradually) in excess; after the reaction is complete, filter, and either evaporate to dryness, or crystallise.

2. Digest freshly precipitated carbonate of barium, in excess, in a hot solution of protiodide of iron; filter and evaporate to dryness; then re-dissolve and crystallise.

3. By saturating hydriodic acid with oxide or carbonate of barium.

_Prop., &c._ A white or greyish-white mass, or acicular crystals (according to the mode of its preparation); very soluble in water and in alcohol; and decomposed by exposure to the air. It has been highly recommended as an alterative, resolvent, and liquefacient, particularly in scrofula, glandular swellings, chronic inflammations, and the other affections in which chloride of barium and iodine are given.--_Dose_, 1/12th to 1/8th gr. (gradually and cautiously increased to 1 gr.), in distilled water, 2 or 3 times a day. Externally, as an ointment (3 or 4 gr., to lard, 1 oz.), as an application to scrofulous swellings. (Biett.) It possesses all the irritant, corrosive, and poisonous properties of the chloride, but in a much more violent degree.

=Barium, Nitrate of.= Ba(NO_{3})_{2}. _Syn._ NITRATE OF BARYTA; BARY'TÆ NI'TRAS, L. _Prep._ As the acetate or chloride of barium, substituting pure nitric acid for acetic or hydrochloric acid.

_Prop., &c._ Transparent, colourless octahedrons, which are anhydrous, insoluble in alcohol, and require about 8 parts of cold water, and about 3 parts of boiling water, for solution.

_Uses._ In _chemistry_, to prepare baryta, and as a test for sulphuric acid and the soluble sulphates; and in _pyrotechny_, to give a green tinge to flame.

=Barium, Oxalate of.= BaC_{2}O_{4}. _Syn._ OX'ALATE OF BARYTA; BARY'TÆ OX'ALAS, L. _Prep._ By precipitating a barium salt with oxalate of ammonium. Very nearly insoluble.

=Barium, Oxide of.= BaO. _Syn._ BARYTA, BARY'TES, CAU'STIC BARYTA*, OX'IDE OF BA''RIUM, PROTOX'IDE OF B., HEAV'Y EARTH; BARYTE, OXIDE DE BARIUM, TERRE PESANTE[dagger], &c., Fr.; BARYT, BARYTERDE, SCHWERERDE, &c., Ger. One of the earths discovered by Scheele in 1774.

_Sources._ Sulphate and carbonate of barium are abundant minerals, forming the 'vein-stone' of many lead mines. It is from the latter that baryta and the barium salts are almost exclusively obtained.

_Prep._ 1. A mixture of carbonate of barium and charcoal (both in fine powder and moistened) is strongly ignited, for some time, in a porcelain, Hessian, or black-lead crucible, and then allowed to cool out of contact with the air, from which it must also be subsequently carefully preserved.

2. (Pure.) Crystallised nitrate of barium is calcined in a capacious covered porcelain or Hessian crucible, at a bright red heat, until red (nitrous) vapours are no longer disengaged, even on raising the temperature; and the residuum, as soon as the temperature has fallen sufficiently, but whilst still warm, is at once transferred to a bottle, as before.

3. M. Rosenthiel's process is founded upon the decomposition of sulphide of barium dissolved in boiling water by oxide of zinc. Caustic baryta and sulphate of zinc are formed.

_Prop._ A greyish-white, spongy, earthy-looking mass, fusible only before the oxyhydrogen blowpipe; highly caustic, corrosive, and alkaline, and slaking, like quick-lime, on the addition of water, but with the evolution of more heat.

=Barium, Peroxide of.= BaO_{2}. _Syn._ DEUTOX'IDE OF BARIUM; BA''RII BINOX'YDUM, &c. L.; BINOXIDE DE BARYUM, &c., Fr. _Prep._ Pure baryta is heated to full redness in a porcelain tube, and a stream of pure dry oxygen passed over it as long as the gas is absorbed.

Baryta, 4 parts, is heated as above in a platinum crucible, and chlorate of potassium, 1 part, gradually added to it; the chloride of potassium formed along with the binoxide being afterwards washed away with cold water.

_Prop., &c._ Grey or greyish-white; with water it forms a hydrate, which is slightly soluble in water, and undecomposed by it in the cold. It is interesting chiefly in its relations with peroxide of hydrogen and the oxygenised acids of M. Thénard.

=Barium, Phosphate of.= Ba(PO_{4})_{2}. _Prep._ In a similar manner to the oxalate, which it resembles in being an almost insoluble white powder.

=Barium, Sulphate of.= BaSO_{4}. _Syn._ SULPHATE OF BARYTA, HEAV'Y SPAR, BOLO''GNIAN S., CAWK (mi); BARY'TÆ SUL'PHAS (Ph. E. & D.), SPA'THIUM PONDERO'SUM, &c., L.; SULFATE DE BARYTE, SPATH PESANT, &c., Fr.; SCHWEFELSAURES BARYT, SCHWERSPATH, &c., Ger. This salt is found native, often in beautiful tabular crystals, but more frequently in white or reddish-white masses. It is also occasionally prepared artificially, as a pigment and chemical, by decomposing a solution of chloride of barium with dilute sulphuric acid, or with a solution of sulphate of sodium; the resulting precipitate being collected, well washed, and dried.

=Prop., &c.= When pure, or free from iron, its powder is white. It is insoluble in water, and nearly insoluble in all other menstrua; before the blowpipe it decrepitates, fuses with great difficulty (by which it is distinguished from the sulphates of strontium and calcium), and ultimately melts into a hard, white enamel. Mixed with charcoal, and heated to redness in a covered crucible, it is reduced to sulphide of barium. It is readily decomposed by fusion with alkaline carbonates; also very slightly so by their cold solutions; but ultimately completely, though slowly, by their boiling solutions. Sp. gr. 4·3 to 4·75.

_Uses._ Chiefly as a pigment (PER'MANENT WHITE), and to adulterate white-lead; for which purposes the native sulphate is commonly well washed, first in very dilute sulphuric acid, and afterwards in pure water, to remove any iron which may contaminate it, and impair its whiteness. It is also used to form sulphide of barium; and, in _pyrotechny_, instead of the more expensive nitrate.

=Barium, Sulphide of.= BaS. _Syn._ SUL'PHIDE OF BARIUM, SUL'PHURET OF BARYTA; BA''RII SULPHURE'TUM, &c., L.; SULFURE DE BARYUM, &c., Fr. _Prep._ Sulphate of barium, well dried and in fine powder, 3 parts; powdered charcoal or powdered coal, 1 part; the mixture is pressed tightly into an earthen crucible, and the cover being fitted on, it is exposed for 1-1/2 to 2 hours, to a bright red heat; after it has cooled, the black mass thus obtained is powdered, and boiled in water, and the resulting solution allowed to crystallise. Some authorities recommend forming the mixed powders into a stiff paste with oil, or oil of turpentine, before calcination; but this is not at all necessary.

_Prop., Uses, &c._ Crystals, thin and nearly colourless plates, containing combined water; very soluble in hot water, less so in cold water; and rapidly decomposed by exposure to the air. It is principally used to form the BARIUM SALTS, and in organic analysis. Care should be taken in its preparation to expose the solution to the air as little as possible. SULPHIDES of a higher grade may be formed by boiling this compound with sulphur; but they possess little practical interest.

=Barium, Sulphite of.= BaSO_{3}. _Syn._ SUL'PHITE OF BARYTA. _Prep._ By testing a soluble barium salt with sodium sulphite, and washing the precipitate. Insoluble.

=Barium, Tartrate of.= BaC_{4}H_{4}O_{6}. _Syn._ TAR'TRATE OF BARYTA. _Prep._ Like that of oxalate of barium. White powder. Slightly soluble.

=BARK.= [Eng., Dan.] _Syn._ COR'TEX, L.; ÉCORCE, Fr.; BAUMRINDE, RINDE, Ger. The rind or exterior covering of vegetables, corresponding to the skin of animals. It consists of the--cu'ticle or epiderm'is--cellular substance, containing colouring matter, &c., and--li'ber, the inner or true bark. The last is formed of woody fibre in great quantity, intermixed with cellular tissue. At the commencement of the annual growth of a tree, the bark separates spontaneously from the wood, in order to make room for the new matter forming beneath. It thus increases by yearly layers, and gradually perishes on the outside, owing to distension, from the growth of the interior portion. Its physiological uses are numerous and important. It is the depository of many of the secretions of plants, and it acts as a living filter, separating secretions from each other, and allowing a part of them to pass off horizontally through the medullary processes on their way to the centre of the tree. But its principal offices appear to be to act as a protection to the tender wood, and as a channel for the sap in its descent from the leaves. "True bark only exists in exogens and gymnosperms; in endogens its place is supplied by cortical integuments, which cannot be separated from the adjacent wood, without violence." (Lindley.)

According to Liebig, the characteristic ingredients found in bark are excrementitious--"substances evidently expelled by the living organism." True wood yields only ·25% to 2% of ash; whilst the bark of some trees give 6, 10, to 15 times more; and these, like the organic constituents, differ materially in their composition and characters.

The uses of different species of bark in medicine and the arts are well known. CINCHONA-BARK is invaluable in fevers; OAK-BARK furnishes the tanner with one of the most important materials of his trade; and the tenacious fibres of other varieties are manufactured into cordage and textile fabrics.

Barks should be collected at that season in which they can be most easily separated from the wood, which, with a few exceptions, is late in the spring; because at this time the active principles deposited in their cells are most abundant. OAK-BARK, collected in spring, contains four times as much astringent matter as that collected in winter.

=Bark.= (In _medicine_.) See CINCHONA.

=Bark.= (In _tanning_.) See OAK.

=Bark, Jes'uit's.= Cinchona-bark.

=Bark, Salt of= (Essential). See EXTRACTS and SALTS.

=BAR'LEY.= _Syn._ HOR'DEUM, L.; ORGE, Fr.; GERSTE, Ger., Anglo-S. A well-known grain, the produce of several species of the genus _hordeum_.

_Var., Cult., &c._ Those principally cultivated in England are--TWO'-ROWED, LONG'-EARED, or COMM'ON BARLEY (_hor'deum dis'tichon_, Linn.); SPRING'-BARLEY, SQUARE'-B., or BERE (_h. vulga''re_, Linn.); and SIX'-ROWED BARLEY, WINTER B., Scotch BERE or BIGG (_h. hexas'tichon_, Linn.). PUT'NEY, SPRAT, or BATT'LEDORE B. (_h. zeocriton_, Linn.), is another species less frequently met with. Of each of the above there are several varieties. In Spain and Sicily, two crops of barley are obtained in a year; but, in countries so far north as Britain, it produces only one, and is a delicate species of grain. In England it is generally adopted as a succession crop on light lands, following turnips or green crops. (Loudon.) The 'yield' per acre varies from 28 to 64 bushels, and is usually from 28 to 40 bushels. The average weight per bushel is 50 to 51 _lbs._; but the best Norfolk and Essex samples weigh 53 to 54 _lbs._ per bushel.

_Comp._ The leading constituents of barley are nearly similar to those of wheat, but it is scarcely so rich in nitrogenised matter. According to Einhof, the ripe SEEDS or GRAINS are composed of--

Meal 70·05
Husk 18·75
Moisture 11·20
------
100·

According to Johnston, average fine BARLEY-MEAL contains--

Starch 68·
Albumen, gluten, &c. 14·
Fatty matter 2·
Ash or saline matter 2·
Water 14·
----
100·

According to Payen, dried barley possesses the following composition--

Nitrogenous matter 12·96
Starch 66·43
Dextrin 10·00
Fatty matter 2·76
Cellulose 4·75
Mineral matter 3·10
------
100·00

According to Dr Ure, the sp. gr. of ENGLISH BARLEY is 1·25 to 1·33 (average, 1·235), and the weight of the husk is about 1-6th; that of BIGG, 1·227 to 1·265, and weight of husk, 2-9ths.

The analyses of the following varieties of barley, gave as the composition of the ashes of the grains:--

---------------------------------------------------
|Unknown |Chevalier| From |Chevalier
| | Barley |Moldavia| Barley
-------------+--------+---------+--------+---------
Potash | 21·14 | 20·77 | 37·55 | 7·70
Soda | | 4·56 | 1·06 | 0·36
Lime | 1·65 | 1·48 | 1·21 | 10·36
Magnesia | 7·26 | 7·45 | 10·17 | 1·26
Sesquioxide | | | |
of iron | 2·13 | 0·51 | 1·02 | 1·46
Sulphuric | | | |
acid | 1·91 | 0·79 | 0·27 | 2·99
Silica | 30·68 | 32·73 | 24·56 | 70·77
Phosphoric | | | |
acid | 28·53 | 31·69 | 38·64 | 1·99
Chloride of | | | |
Sodium | 1·10 | | 1·47 | 1·10
---------------------------------------------------

In the 'Journal of the Agricultural Society' for 1873 is a report by Messrs Lawes and Gilbert of twenty years' experiments with barley. The soil of a field at Rothampstead, in which the barley had been grown for twenty years, consisted of heavy loam, with a subsoil of clay resting on chalk, and was previous to the barley being planted almost exhausted by cropping. The produce was found to be greatest during the absence of drought and sudden alterations of temperature, the rather cool but uniform season of 1854 giving the heaviest crops. The yield from farm-yard manure and nitrate of soda was found in dry seasons to be rather larger than that from ammonia salts. Barley manured with phosphates was found to ripen one to two weeks earlier than when the phosphate was omitted.

The average produce per acre of a few of the principal plots is given below. The "ammonium salts" are stated to be a mixture of equal parts of sulphate and chloride; the "alkali salts" consist of the sulphates of potassium, sodium, and magnesium; the "cinerials" consist of alkali salts, plus superphosphate:

KEY:
A: Dressed Corn.
B: Straw and Chaff.
C: Total Produce.
D: Corn to 100 Straw.
E: Weight per Bushel of Dressed Corn.
F: Produce of second 10 yrs. over or under first 10 yrs.

-----------------------------+--------+------+----+----+----+--------
Manures per Acre. | A | B | C | D | E | F
-----------------------------+--------+------+----+----+----+--------
|bushels.| cwts.|lbs.| |lbs.|per cwt.
| | | | | |
Unmanured | 20 |11-3/4|2454|86·6|52·3|- 23·6
Mixed cinerials | 27-1/2 |14-3/8|3162|96·4|53·4|- 20·2
Ammonium salts, 200 lbs. | 32-1/2 |18-1/2|3919|89·2|52·1|- 9·7
Ammonium salts, 200 lbs., and| | | | | |
alkali salts | 35 |20-3/4|4317|86·3|52·8|- 5·3
Ammonium salts, 200 lbs., and| | | | | |
superphosphate | 47 |27-5/8|5760|86·8|53·5|+ 2·7
Ammonium salts, 200 lbs., and| | | | | |
cinerials | 46-1/4 |28-1/2|5817|83·2|54·0|- ·3
Rape cake (mean 1300 lbs.) | 45-1/4 |26-7/8|5571|87·3|53·8|
Farmyard manure, 14 tons | 48-1/4 |28-1/4|5933|88·5|54·3|+ 14·8
-----------------------------+--------+------+----+----+----+--------

The authors direct attention to the results obtained by using the cinerial manure alone, as illustrating the unsoundness of the old "mineral theory," according to which plants were supposed to possess a sufficient source of nitrogen in the atmosphere. They found a greater crop yielded by barley than wheat, when no manures were employed, as well as when cinerials were employed, a fact which they attribute to barley being better able than wheat to supply itself with nitrogen, notwithstanding the deeper roots of the latter. They state that with both wheat and barley the produce is slowly falling off under these circumstances. With ammonium salts alone, and with nitrate of sodium alone, there is much less falling off than when no nitrogenous manure is used. The falling off was least with the nitrate. The nitrate gives a rather larger crop for the same amount of nitrogen supplied, and they found this to hold when both nitrate and ammonia are applied with cinerials. The addition of superphosphate to ammonium salts or sodium nitrate greatly increases the produce; the further addition of potassium, sodium, and magnesium salts they found almost without effect.

The inference was that the barley had obtained an ample supply of potash from the natural soil, but an insufficient supply of phosphoric acid.

When ammonium salts are used alone, and the quantity of ammonia does not exceed 50 lbs. per acre, 3·68 lbs. of ammonia will yield an average increase of 1 bushel of corn and 63 _lbs._ of straw--total, 115 _lbs._; the extremes in 20 years were 2·25-18·05 _lbs._ When ammonium salts are applied with superphosphate, 2·21 _lbs._ of ammonia will produce the same result; the extremes were 1·47-5·36 _lbs._

Silicate of sodium had been applied for eight years and a half to half the barley plots receiving ammonia; no increase has resulted where ammonia and superphosphate are employed; but on the other three plots an increase had taken place, which, in the case of the plot receiving only ammonia and alkali salts, is very considerable.

The authors think this irregular reaction seems to show that the silicate has not produced its effect by furnishing silica to the crop, but by some reaction upon the plant-food of the soil. The rape cake supplied much more nitrogen than the ammonium salts, and also some phosphates and potash. Rape cake alone gives a better return than either ammonium salts or sodium nitrate applied alone; but when the three manures are mixed with superphosphate, the results for equal amounts of nitrogen show the rape cake to be decidedly inferior. From the above experiments it is inferred that a supply of carbonaceous matter does not increase the crop of barley.

A farm-yard manure containing about 0·64 per cent. of nitrogen supplied far more plant food than any of the other manures. On an average of twenty years it was found that about 8 lbs. of ammonia in the form of dung would produce a bushel of barley, with its equivalent of straw.

In all cases which were comparable it was found that barley appropriates more of the nitrogenous manure than wheat, save with farmyard manure. A large amount of nitrogen applied by manure is not taken up by the crop. Experiments in the barley field proved that large residues from ammonium salts and sodium nitrate show a small but distinct effect upon succeeding crops, the influence extending over many years. From an examination of the drainage waters from lands dressed with the nitrates of ammonium and sodium, the authors conclude that ammonium salts, as well as sodium nitrate, will be more economically applied in the spring than in the winter. Manures containing organic nitrogen are clearly not so liable to loss from drainage.

Experiments were made on the growth of barley after turnips, and also in an ordinary four-course rotation. After growing turnips ten years consecutively with purely cinerial manures, and carting off the produce, the yield of barley was much smaller than in the experimental field, where barley was grown after barley. The turnips, though very small crops, had exhausted the soil of nitrogen to a greater extent than corn crops would have done. On one plot where rape cake had been applied to the turnips, the produce of barley was 8-1/4 bushels more than when none had been used. In the rotation experiments barley was grown after turnips (carted off), and was followed by beans and wheat. In one series all the crops were unmanured; in another the turnips received superphosphate; in a third the turnips received an abundant cinerial and nitrogenous manure.

The mean produce of the six crops of barley obtained in twenty-four years of rotation was as follows:

------------------------------------------------
|Dressed | Straw and
Character of Rotation. | Corn. | Chaff.
--------------------------+---------+-----------
| bushels.| cwt.
Unmanured continuously | 38-3/8 | 21-3/4
Superphosphate for turnips| |
only | 29-3/8 | 16-1/2
Mixed manure for turnips | |
only | 44-3/8 | 25-1/4
--------------------------+---------+-----------
Mean produce of unmanured |} |
barley in barley |} 21-1/2 | 12-1/8
field during the same |} |
season |} |
------------------------------------------------

The unmanured turnips were so very small in quantity, that the barley in the first series was practically grown after a fallow; this barley, however, was a much larger crop than that grown after turnips manured with superphosphate only, the available nitrogen of the soil in this case being exhausted by the turnips.

In the last series the residue of the abundant manure applied to the turnip crop suffices to produce a good crop of barley.

_Qual., Uses, &c._ Its employment and value as food, and in the manufacture of malt, are well known. It forms good wholesome bread well adapted for persons who live luxuriously; but which, for the abstemious and the delicate, is inferior to that made of wheat, as it is rather less nutritious, and less easy of digestion, and commonly proves laxative to those unaccustomed to its use. Barley-flour and barley-meal are also more perishable than wheat-flour; being very apt to acquire a hot nauseous taste, which even the heat of the oven does not remove. In a medical point of view, barley is regarded as the mildest and least irritating of the cereals. It has always been in high estimation as a demulcent and emollient. The decoction (BAR'LEY-WATER), made with pearl barley, is a common and useful drink in inflammatory diseases, particularly in those of the chest and urinary organs. Among the Ancients, decoctions of barley ([Greek: krathê]) were the principal aliments and medicines employed in acute diseases.

Barley was extensively cultivated by the Romans and many other nations of antiquity, as well as by the ancient inhabitants of Gaul. The Greeks are said to have trained their athletes on it.

The best tests of the genuineness of barley are its colour, freedom from dust, grit, and insects. The microscope will lead to the detection of any cheaper grains if mixed with it. It is rarely adulterated, although it is said to be extensively used for the purpose of sophisticating wheat, annatto, and roll liquorice.

=Barley, Cau'stic.= Sabadilla.

=Barley, Pat'ent.= _Syn._ FARI'NA HOR'DEI, L. Pearl barley reduced to fine powder by grinding in a mill.

=Barley, Pearl.= _Syn._ PEARL'ED BARLEY*; HOR'DEUM DECORTICATUM (B. P.), L.; ORGE PERLÉ, Fr.; PERLENGRAUPEN, Ger. The seeds of _hordeum distichon_ deprived of the husks. That of commerce is usually made by steaming spring-barley, to soften the skin, then drying it, and grinding it in a mill with the stones set wide apart, so as to round and polish the grains, and to separate the whole of the husk except that left in the furrow of the seed. SCOTCH PEARL-BARLEY and FRENCH BARLEY resemble the last, but are smaller, being generally made from winter-barley or bigg. FARO DE ORZO is another variety made from sprat-barley. See BARLEY (_above_).

=Barley, Scotch.= _Syn._ HULLED BARLEY[double-dagger], POT-B.[double-dagger]; HOR'DEUM MUNDA'TUM, L.; ORGE MONDÉ, Fr.; GERSTENGRAUPEN, GRAUPEN, Ger. The grains deprived of the husk by a mill, as noticed above, but less completely, and without rounding them.

=BAR'LEY SUGAR.= See CONFECTIONERY, and SUGAR.

=BARM.= See YEAST.

=BAROM'ETER= (_baros_, weight; _metron_, measure). _Syn._ WEATHER-GLASS[double-dagger]; BAROM'ETRUM, L.; BAROMÈTRE, Fr.; BAROMETER, WETTERGLAS, Ger. An instrument for measuring the weight or pressure of the atmosphere. It was invented by Torricelli, of Florence, A.D. 1643.

The barometer is made of several forms, but the principle of its construction, with the exception of the aneroid barometer, is the same in each, and essentially consists of a column of fluid (usually mercury) supported in vacuo, in a glass tube, by the pressure of the atmosphere on its surface. The annexed figures exhibit the principal varieties at present known; several of which have been proposed with the view of improving the original instrument, either by increasing its range, or its portability. None, however, equal in simplicity, cheapness, and usefulness, the old forms proposed by Torricelli, and represented by the figs. 1 & 2. To avoid confusion, the graduated scales and cases of the instruments are not shown.

1. Torricelli's cistern barometer.
2. " syphon "
3. Huygen's barometer.
4. " " modified.
5. Wheel barometer.
6. Bernoulli's syphon barometer.
7. Aminton's conical "
8. Gay Lussac's "
9. " " " modified by M. Bunten.
_a_, Tube containing a column of mercury.
_b_, Mercurial cistern.
_c_, A column of mercury supporting another of water, _d_.
_e_, _e_, Weights, one of which floats on the surface of the mercury,
and by means of the cord _f_ moves the index _g_.
_h_, Graduated dial.
_k_, Capillary hole drilled laterally to admit air.]

The construction of a barometer requires the utmost skill and care of a practised artist, and will therefore be seldom undertaken by the amateur or experimentalist--a fact which renders it unnecessary for us to enter into the details here. In the choice of his instrument the purchaser must greatly depend on the known experience and integrity of the manufacturer; as nothing but lengthened use, and frequent comparisons with other instruments, can possibly prove its excellence. An ordinary barometer, however carefully made, is found to suffer gradual deterioration, from the external air insinuating itself between the mercury and the glass tube, by which the perfection of the vacuum is destroyed. Various plans have been proposed to remedy this inconvenience and source of error. Prof. Daniell forms the bottom part of the tube, to the extent of about 1/3rd of an inch, of solid platinum, welded to the glass. This plan has proved completely satisfactory. Dr Ure proposes the use of platinum-foil for the same purpose. Before purchasing an instrument it is as well to ascertain that this has been done. In those called 'STANDARD BAROMETERS' the scale is movable and adjustable by a delicate screw, so as to enable the observer to bring the lower point or zero (0) of the scale coincident with the surface of the mercury in the cistern. Exact contact is readily effected by making the point, and its image as seen by reflection from the surface of the mercury, to coincide. In this case the cistern is made of glass. Provided the ivory scale be connected with the zero-point with a strip of brass, correction as to temperature is very nearly effected by this simple adjustment. The WHEEL-BAROMETER is chiefly serviceable as a domestic or land weather-glass.

Of the many forms of mercurial barometer, that perhaps known as Fortin's is the best. In this instrument the cistern and the lower portion of the tubes is shown in the annexed figure.

"The cistern is made of boxwood, with a movable leather bottom _b b_, and a glass cylinder, _b_, is inserted into it above, all except the glass being encased in brass. In the bottom of the brass box a screw, C, works on the upper end of which the leather rests, so that by elevating or depressing this screw, the bottom of the cistern, and with it the cistern level of the mercury, can also be raised or depressed at pleasure. A small ivory pin, _p_, ending in a point is fixed to the upper frame of the cistern, and when an observation is made, the surface of the mercury is made to coincide with the point of the pin as the standard level from which the barometric column is to be measured. The tube of the barometer, the upper part of which is shown in the lower figure, is enclosed in one of brass, which has two directly opposite slits in it for showing the height of the column, and on the sides of these the graduation is marked. A brass collar, _d, d_, slides upon the tube with a vernier, _v, v_, marked on it for reading the height with the greatest exactness and in which two oblong holes are cut, a little wider than the slits in the brass tube. When a reading is taken the collar is so placed that the last streak of light is cut off by the two upper edges of the holes or until they form a tangent to the convex mercurial curve. By this means the observer is sure that his eye is on a level with the top of the column and that the reading is taken exactly for this point. Fortin's barometer is generally arranged so as to be portable, in which case the screw, _c_, is sent in until the mercury fills the whole cistern, by which the air is kept from entering the tube during transport, the leather yielding sufficiently at the same time to allow for expansion for increase of temperature. It packs in a case which serves as a tripod when the instrument is mounted for use. On this tripod it is suspended about the middle, swinging upon two axles at right angles to each other, so that the cistern may act the part of a plummet, in keeping the tube vertical--the position essential to all measurements."[107]

[Footnote 107: Chambers's 'Encyclopædia.']

_How to Manage a Barometer._--It is of the first importance to have the instrument hung perfectly perpendicular. This is best effected by means of a plummet line. It should be placed in a good light, but protected from direct sunlight and also from rain. If air should accidentally find its way into a common cistern barometer, it may be got rid of by first fixing the ivory piston, so as to prevent the escape of the mercury, then by means of the screw raising the mercurial column nearly to the top of the tube, then by slowly inverting the instrument and tapping the cistern gently, the air may then perhaps ascend to the cistern and thus escape. In transporting a barometer from place to place it is best to carry it by hand; and if packed it is almost needless to say that the float must be firmly fixed and the mercurial column raised by means of the screw, so as to prevent any escape of the metal.

_Reading the Barometer._--The mercury in the cistern must first be brought by means of the screw to the 'zero,' and then the vernier must be screwed up so that its horizontal edge forms a tangent to the mercurial curve. The vernier is an instrument for reading off the graduated scale of the barometer correctly to 1/100th or 1/500th of an inch.

Buchan gives the following description of the vernier and of the method of using it: "It consists (see figures _a_ and _b_) of a piece similar to the scale of the barometer along which it slides. It will be observed from figure _a_ that ten divisions of the vernier are exactly equal to eleven divisions of the scale, that is, to eleven tenths of an inch. Hence each division of the vernier is equal to a tenth of an inch, together with a tenth of a tenth, or a hundredth, or to ten hundredths, and one hundredth, that is, to eleven hundredths of an inch. Similarly two divisions of the vernier are equal to twenty-two hundredths of an inch, which expressed as a decimal fraction is 0·22 inch, three divisions of the vernier is 0·33 inch, &c. Suppose the vernier set as previously described--that is, having the zero line of the vernier a tangent to the convex curve of the mercury in the column. If the vernier and scale occupy the relative positions as in figure _a_, then the height of the barometer is 30·00 inches, but if they stand as in figure _b_, we set about reading it in this way: (1) The zero of the vernier being between 29 and 30, the reading is more than 29 inches, but less than 30 inches, and we obtain the first figure 29 inches. (2) Counting the tenths of an inch from 29 upwards we find that the vernier indicates more than seven tenths and less than eight tenths, giving the second figure seven tenths or 0·7 inch. (3) Casting the eye down the scale to see the point at which a division of the scale and a division of the vernier lie in one and the same straight line, we observe this to take place at line 9 of the vernier; this gives this last figure nine hundredths or 0·09 inch, and placing all these figures in one line we find that the height of the barometer is 29·79 inches. This sort of vernier gives readings true to the hundredth of an inch. If the inch be divided into half tenths or twentieths, and twenty-five divisions of the vernier equal twenty-four divisions of the scale, it follows that the difference of these divisions is two thousandths of an inch."

A still more divided vernier is always used with the best barometers, and though a little troublesome to read at first, yet if the method of reading the simpler one just described be understood, the difficulty will be easily overcome.

_Uses, &c._ The barometer is employed for ascertaining the amount of atmospherical refraction in astronomical calculations, for measuring altitudes, and in prognosticating the weather. For the last purpose, on land, it sometimes proves a false prophet; but at sea, its monitions are highly trustworthy. As a mere weather-glass, the indications, as read off from the scale of the instrument, are generally sufficiently accurate; but in all observations connected with meteorology, altitudes, astronomy, &c., certain corrections must be made; the height of the mercury being influenced both by the size of the tube and by the temperature of the air by which it is surrounded, as well as by variations in the weight or pressure of the atmosphere. (See _below_.)

_Barometrical Corrections_:--

1. As to CAPILLARITY:--This applies to all cistern-barometers formed of tubes of very small diameters, owing to the mercury assuming a convex surface in the tube. As the tube increases in diameter, so the depression of the mercury lessens. Hence, the "interior diameter" of a barometer "should, in every case, exceed one-fourth of an inch." (Brande.) Syphon barometers that have each of their legs of equal size, require no correction, as the depression is equal at both ends.

TABLE _of Barometrical Corrections for_ CAPILLARITY,
_from the_ 'Encycl. Brit.'

--------------------+------------------
Diam. of Tube. | Depression.
--------------------+------------------
·10 inch. | ·1403 inch. +
·15 " | ·0863 "
·20 " | ·0581 "
·25 " | ·0407 "
·30 " | ·0292 "
·35 " | ·0211 "
·40 " | ·0153 "
·45 " | ·0112 "
·50 " | ·0083 "
·60 " | ·0044 "
·70 " | ·0023 "
·80 " | ·0012 "
--------------------+------------------

2. As to TEMPERATURE:--These depend on the expansion of the mercury, and of the scale on which the divisions are marked. The rule for reducing an observed height to the corresponding height at the freezing-point, or 32° Fahr., the usual standard temperature, is--Subtract 1·10000th part of the observed height of the barometer for every degree of Fahr. above 32° at the time of the observation. Or--

(obs. t. - 32) × obs. h. × ·0001 = corr. req.

_Measurement of Heights by the Barometer._--When a barometer is at the foot of a mountain, the pressure it sustains is greater than that to which it is subjected at the top, by the weight of the column of air intervening between the top and the bottom.

The height can be obtained from the following table by calculating the number of feet which must have been ascended to cause the observed fall; and then making a correction for temperature by multiplying the number obtained from the table, which may be called A, by the following formula: _t_ is the temperature of the lower and _t'_ of the upper station:--

1 × ((_t_ + _t'_ - 64) / ·900) × A.

To lower the barometer from 31 in. to 30 = 857 feet must be ascended.
" " " 30 " 29 = 886 " "
" " " 29 " 28 = 918 " "
" " " 28 " 27 = 951 " "
" " " 27 " 26 = 986 " "
" " " 26 " 25 = 1025 " "
" " " 25 " 24 = 1068 " "
" " " 24 " 23 = 1113 " "
" " " 23 " 22 = 1161 " "
" " " 22 " 21 = 1216 " "
" " " 21 " 20 = 1276 " "
" " " 20 " 19 = 1341 " "
" " " 19 " 18 = 1413 " "

A very complex formula is given by mathematicians for finding very nearly the true height of a mountain from barometrical and thermometrical observations made at its base and summit. The following rule by Mr Ellis will be found to give very nearly the same results:--Multiply the difference of the barometric readings by 52,400, and divide by the sum of the barometric readings. If the result be 1000, 2000, 3000, 4000, or 5000, add 0, 0·2, 6, 14, respectively. Subtract 2-1/3rd times the difference of the temperature of the mercury. Multiply the remainder by a number obtained by adding 836 to the sum of the temperatures of the air and dividing by 900. A correction must also be given for latitude, which can be done by the annexed table.

---------+--------++---------+---------
Latitude.| Factor.||Latitude.| Factor.
---------+--------++--------+----------
80 | 0·99751|| 35 | 1·00090
75 | 0·99770|| 30 | 1·00265
70 | 0·99797|| 25 | 1·00170
65 | 0·99830|| 20 | 1·00203
60 | 0·99868|| 15 | 1·00230
55 | 0·99910|| 10 | 1·00249
50 | 0·99954|| 5 | 1·00261
45 | 1·00000|| 0 | 1·00265
40 | 1·00046|| |
---------+--------++---------+---------

Fortin's and Gay-Lussac's barometers are employed for measuring heights. The aneroid can be used for altitudes reaching to 5000 feet. A delicate instrument will register for as small an ascent as 4 feet.

_The Barometer as a Weather-glass._--Generally speaking when the mercurial column in the barometer falls, 'rain' is indicated, and 'fair weather' when it rises. When it continues steady, a continuance of the weather at the time is regarded as the forecast; when low, the weather is generally broken or bad; and when high, it is fair and settled. A storm is usually preceded by a sudden fall in the mercurial column, the violence of the storm being in proportion to the suddenness of the fall. An unsteady barometer indicates an unsettled condition of weather, whilst a gradual change in it indicates the approach of some permanent condition of it. The state and direction of the wind has also to be taken into consideration when studying the changes of the barometer, and forms an important element in the calculations of the meteorologist, each different wind indicating variations of weather. The connection between changes of weather and the pressure of the atmosphere does not seem to have been satisfactorily established.