BAR 



BAR 



a more impure alkali, made in this coun- 

 try by burning various sea-weeds. 



BA'RIUM (/Sapi/f, heavy). A peculiar 

 metal, the basis of the alkaline oxide or 

 earth barytes, named from the great 

 density of its compounds. 



BARK OF PLANTS. The external 

 envelope of trees and shrubs. It was 

 formerly distinguished into an external 

 cortical or cellular integument, and an 

 internal or fibrous portion, called liber. 

 More recently, bark has been distin- 

 guished into four portions ; — 



1. Epidermis. The external and cel- 

 lular envelope, continuous with the epi- 

 dermis of the leaves. This is never 

 renewed ; the following parts increase 

 by successive additions to their in- 

 terior. 



2. Epi-phlceum (eTri, upon, (p\oi6^, 

 bark). A cellular portion lying imme- 

 diately under the epidermis. Cork is the 

 epiphloeum of the Quercus suber. 



3. Meso-phloeum (fxeaoi, middle, (pXoioi, 

 bark). A cellular portion, lying imme- 

 diately under the epiphloeum. This por- 

 t'on differs from the preceding in the 

 direction of its cells. 



4. Endo-phloeum {evbov, within, cpXotoi, 

 bark). The liber, part of which is cellu- 

 lar, part woody. 



BA'ROLITE {/3apv9, heavy, \/0o?, a 

 stone). Heavy stone ; a carbonate of 

 baryta. 



BARO'METER (ySapop, weight, yue- 

 rpov, a measure). An instrument for 

 measuring the weight or pressure of the 

 atmosphere, by balancing a column of air 

 against a column of mercury ; and, by 

 that test, measuring heights and depths, 

 determining variations in the state of the 

 air, and foretelling changes in the wea- 

 ther. "When employed for determining 

 the degree of rarefaction attained in 

 the receiver of an air-pump, it is called 

 a barometer-gauge. 



1. The cistern barometer is a ToTxicel- 

 lian tube, whose open end is immersed 

 in a wider cistern of mercury. The zero 

 point is on a level with the surface of the 

 mercury. This is the oldest form of the 

 instrument. 



2. The common barometer is a Torri- 

 cellian tube, whose open end is turned 

 up and is of a spherical form. The 

 globe performs the office of the cistern 

 described in the preceding barometer : 

 the scale is graduated from the same 

 point in both these instruments. 



3. De Luc's syphon barometer consists 

 of a glass tube bent upwards so as to 



48 



form two parallel legs : the longer is her- 

 metically sealed, and constitutes the 

 Torricellian tube ; the shorter is open, 

 and on the surface of the mercury the 

 pressure of the atmosphere is exerted. 

 The difference between the levels in the 

 two legs is the barometric height. 



BA'ROMETZ {baronez, Russian, a 

 little lamb). A species of Aspidium, or 

 shield fern, which, from its procumbent 

 position and shaggy appearance, has ac- 

 quired the name of 'Scythian lamb," 

 and the credit of possessing some of the 

 properties of this animal. 



BA'ROSCOPE (/5a'po9, weight, o-KOTrew, 

 to perceive). A perceiver of weight ; a 

 term sometimes applied to the barometer. 

 Etymologically speaking, a baroscope is 

 not a barometer, though a barometer is a 

 baroscope. 



BA'RRAS, or GALIPOT. The resin- 

 ous incrustation on the wounds made in 

 fir-trees. 



BA'RRIER REEF. A coral produc- 

 tion, similar to the Atoll, or coral island. 

 It runs parallel with the shores of a 

 larger island or continent, separated, 

 however, from the land by a broad and 

 deep lagoon channel, and having the 

 outer side as steep as in the lagoon 

 islands. 



BA'RTER. A rule in Arithmetic, by 

 which the values of commodities of dif- 

 ferent kinds are compared, for the pur- 

 pose of exchange. 



BARYSTRO'NTIANITE. Stromnite. 

 A mineral found in veins, or rather 

 nests, accompanied by galena, at Strom- 

 ness, in Orkney. It consists of the car- 

 bonates of strontia and of lime, sulphate 

 of baryta, and oxide of iron. 



BARY'TES {papi,^, heavy). Baryta. 

 The protoxide of barium, an alkaline 

 earth, the heaviest of all the earths, and 

 a violent poison. The native sulphate is 

 called heavy spar, or cawk. The native 

 carbonate has been named, after Dr. 

 Withering, its discoverer, wilherite. A 

 solution of barytes in water is called 

 barytes water, and is used as a chemical 

 re-agent. 



BARY'TIN. A new vegetable base, 

 discovered in the rhizome of Veratrum 

 album, and named in consequence of its 

 being precipitated from its solution, like 

 baryta. See Jervin. 



BARY'TO-CALCITE. A mineral 

 found in Cumberland, consisting of the 

 carbonates of baryta and of lime, with 

 an outer coating of sulphate of baryta. 



BA'RYTON (/3apvr, heavy, tovo^, 



