VIB 



VIN 



She is thought to be 225 millions of 

 miles distant from the sun. 



VESU'VIAN or I'DOCRASE. A 

 stone, generally of a reddish -brown co- 

 lour, similar in appearance to common 

 garnet. It is found crystallized among 

 substances thrown out by volcanoes, and, 

 as its name indicates, particularly by 

 Mount Vesuvius. The rare blue variety 

 is found at Sonneland, in Telleraark in 

 Norway. At Naples it is cut into ring- 

 stones. 



VEXI'LLUM (dim. of velum, a veil). 

 A standard or small banner ; a term ap- 

 plied to the upper petal of a papilionace- 

 ous corolla, from its erect and expanded 

 state. For the use of the term vexillary, 

 see Vernation. 



VIBRATING SURFACES. The phe- 

 nomena of the production of figures by 

 strewing sand on vibrating surfaces, com- 

 monly called acoustic figures, have been 

 noticed under the terms " Sonorous 

 Figures" and "Nodal Lines." Mr. 

 Wheatstone shows that all the figures of 

 these vibrating surfaces are the resultants 

 of very simple modes of oscillation, oc- 

 curring isochronously, and superposed 

 upon one another; the resultant figure 

 varying with the component modes of 

 the vibration, the number of the super- 

 positions, and the angles at which they 

 are superposed. When the vibrations of 

 the superposed modes are unequal in 

 intensity, there is formed a figure inter- 

 mediate between the perfect resultant 

 and one of its compounds : these figures 

 are called imperfect resultants. 



VIBRATION {vibro, to quiver). Os- 

 cillation. A term applied to those mo- 

 tions of a body, by which, when its con- 

 stituent particles have been disturbed 

 from their equilibriums, they return to a 

 state of repose. This is effected by the 

 particles alternately approaching the posi- 

 tion of rest and receding from it, until, 

 after some time, the equilibrium is re- 

 stored. See Interval. 



1. The Theory of Vibrations has been 

 adopted for explaining the phenomena 

 of light, which are supposed to depend 

 on the vibrations, or undulations, of a fluid 

 called eiher, diffused through all nature, 

 and set in motion by the presence of 

 luminous bodies. See Emission. 



2. Bodies of a linear form are capable 

 of exhibiting three kinds of vibration, 

 the transverse, the longitudinal, and the 

 rotatory. 1. If a piece of whip-cord be 

 strained tight and firmly held at each 

 end, and be then pulled in the middle 



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from its position of rest, and suddenly 

 let go, it undergoes a series of transverse 

 vibrations. 2. If the cord be held at one 

 end, and a weight attached to the other 

 end be raised, and then let go, a series 

 of longitudinal vibrations is produced. 

 3. Lastly, if the cord be twisted by 

 means of the weight, and the weight be 

 suddenly allowed to fall, the cord exhi- 

 bits a series of rotatory vibrations. 



3. Vibrations, co-existence of. This, 

 and the equivalent term superposition of 

 vibrations, denote a principle in mecha- 

 nics, which seems to be only a particular 

 case of what might be called the co- 

 existence or superposition of small 

 changes of any kind. For instance, two 

 stones are dropped into water at two 

 different places, and at a certain time, 

 on a certain part of the surface ; in this 

 case, the resulting waves cross one an- 

 other. If there be a particle which is at 

 the same time raised on both waves, 

 say a tenth of an inch from one, and 

 three-tenths of an inch from the other, 

 that particle will altogether be raised four 

 tenths of an inch, or insensibly near to 

 it. — Pen. Cycl. 



VIBRIO'NIDiE. A tribe of animal- 

 cules, named from the genus vibrio, and 

 commonly known as microscopic eels. 

 One species, the vibrio tritici, is parasitic 

 on wheat, and it has been computed that 

 50,000 of them might be contained in 

 a single grain of wheat. 



Vl'CIEiE {vicia, the vetch). A ttibe 

 of leguminous plants, having a papilio- 

 naceous corolla, diadelphous stamens, 

 continuous legumes, thick farinaceous 

 cotyledons, not changing in germination, 

 and a radicle curved inward. They in- 

 clude the vetches, the bean, the pea, &c. 



VILLOSITY {villosus, shaggy). Shag- 

 giness ; a term denoting that state of 

 hairiness in plants, in which the hairs 

 are very long, very soft, erect, and 

 straight, as in epilobium hirsutum. 

 When in excess, the hairs are termed 

 crini. 



VI MEN. A long and flexible shoot of 

 plants. This word is, however, seldom 

 used, the adjective being employed in- 

 stead: thus, we say, rami viminei, or 

 caulis vimineus, and so on. See Virgate. 



VI'NCULUM. Literally, a bond ; and, 

 hence, the term denotes, in algebra, a 

 line sometimes used instead of brackets, 

 and drawn above qu antit ies which are 

 connected ; thus a — b — c is the s ame as 

 a — (6 — c) ; and a — 6 + c x d — e 

 means the same as (a — 6 + c) x id — e). 

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