V I R 74 



was first found in Ionia. There are seven 

 indigenous species, of which the sweet- 

 scented violet, with its seven or eight 

 varieties, is the greatest favourite. The 

 pansy or heart's-ease is also well known. 

 2. In Mii/sic, a viola is a tenor violin. 



VIOLA'CEOTS, Lat. violaceus. An epithet 

 designating a bluish purple colour like 

 that of the violet. 



VI'OLET. 1. In botany, see VIOLA. 2. 



Violet colour. A mixture of red and blue. 



VIOL'IN. A common musical instrument, 

 less than the viol. 



VIOLONCEL'LO. The Italian name of our 

 fifth violin, which comes between the 

 viola di braccio (arm viol) and the double 

 bass, both as to ton* and size. The notes 

 for the violoncello are written on the F 

 or bass clef, and it generally accompanies 

 the double bass. 



VIOL'ONE (Ital.). The English double 

 bass viol, the largest musical instrument 

 played with a bow. It is principally used 

 to sustain the harmony. 



"VI'FEKA, Viper. A genus of true ser- 

 pents (serpentia}. There are several spe- 

 cies. The minute viper (V. brachyura, 

 Cuv.;, is celebrated for the intensity of 

 its poison, and is truly one of the most 

 terrible of the genus. The Asp of Egypt, or 

 Cleopatra's asp. (the Coluber naja, Lin.), 

 was held in great veneration by the Egyp- 

 tians. The jugglers, by pressing on the 

 nape of the neck with the finger, throw it 

 into a kind of catalepsy, which renders it 

 stiff, or turns it into a rod, as they term it. 



VIR'GO. Virgin. The sixth sign of the 

 zodiac. 



VIR'TUAL. 1. A term signifying poten- 

 tial, and understood of something which 

 acts by a secret invisible cause, in oppo- 

 sition to what is sensible and palpable. 

 2. In mechanics, if any number of 

 forces applied to the different parts of a 

 system be in equilibrium r 

 and these points admit of J 



displacement, the circum- /' 



stances of their mutual re- / { 



lation and dependance re- 

 maining unaltered ; and fur- 

 ther, if the nature of the 

 system, and the forces ap- 

 plied to it, be such that the 

 points of application being 

 thus altered according to 

 certain conditions, the equi- 

 librium remains ; then there 

 exists the following re- 

 markable relation between 

 the forces and the distances 

 through which these points 

 of application have been 

 made to move. If from either extremity 

 P of the line P P' representing the ex- 

 ceeding small displacement of any point 

 of application P, a perpendicular Pm be 

 dr&wc. froin the direction P,of the force 



! V I T 



before its displacement ; and the line I'm 

 intercepted between the foot of the pf-r- 

 pendicular m, and the point P, be called 

 the virtual velocity of the force P ; theu, 

 each force of the system being multiplied 

 by its virtual velocity, similarly taken, the 

 sum of these products in respect to the 

 points of application which are made by 

 the displacement of the system to move 

 towards the direction of the forces im- 

 pressed upon them, shall be equal to the 

 sum of those taken in respect to those 

 points which are made to move from that 

 direction. This very important principle 



is called that of virtual velocities. 3. 



In optics, the point from which rays, hav- 

 ing been rendered divergent by reflection 

 or refraction, appear to issue. 



VIRTCO'SO, (Ital.). A man skilled in 

 matters of antique curiosity, fine arts, &c. 



VI'RITS. A poison. The term applies 

 in pathology, to designate the matter of a 

 disease capable of producing that disease 

 in a healthy individual by inoculation 

 or absorption. 



Vis. A Latin word for power. Vis a 

 tergo, amoving power acting from behind. 

 Vis titm, the vital power or energy. Vis 

 inertias, the power of inertness ; the force 

 with which matter resists change of 

 place. Via insita, innate force essential 

 to the natural state of a body. 



VIS'CERA, Lat. pi. of visats. In anatomy, 

 the organs contained in any of the three 

 great cavities, especially the thorax and 

 abdomen. 



VIS'COCXT, Lat. vicecomes. In heraldry, 

 a title of nobility next to earl. In law, a 

 sheriff. 



Vis'crsi. The mistletoe. A genus of 

 parasitical plants. Divecia Tetrantiria. 

 Name from ,>?or fiio-zo;, the fruit of the 

 V. album, found in Britain. The V. quer- 

 cinus was held in high esteem by the 

 Druids. See MISTLETOE. 



VISH'XU. In HitM Theology, the second 

 person of the Trinity. 



VIS'ION , from risus. The function which 

 enables us to perceive the magnitude, 

 figure, colour, distance, &c., of bodies. 

 The organs which compose the apparatus 

 of vision enter into action under the in- 

 fluence of the particular excitant which 

 we call light, generally regarded as an 

 excessively subtle fluid, emanating from 

 bodies denominated luminous, as the sun. 

 fixed stars, bodies in a state of ignition , &c 



VIS'CAL. In perspective, the visual poim 

 is that in the horizontal line in which all 

 the ocular rays unite. Visual rays are 

 then imagined to come from the object to 

 the eye. 



VI'TAL VES'SELS. Applied by Schultz to 

 certain vessels in plants, especially near 

 the surface, conveying latex, which he 

 calls a vital fluid. Also, the milk-Yesstbi 

 of spurges. 



