VALVASOR. 



VANADIUM. 



and wages ruse, the value of each would rise in an equal proportion, 

 and the article* would continue to exchange for each other aa before. 

 But if the cloth wen produced almost entirely by machinery and tho 

 silk entirely by manual labour, a rise of wages would soaroely aJbet the 

 former at all, while it would add materially to the cost of fiaHmimg 

 the Utter. They would therefore no longer exchange for each other, 

 r. in other words, their relative value would be altered. The general 

 law of such variations is thus stated by Mr. Uioardo, namely, that in 

 the event of a rise in the price of labour, " only those commodities 

 would rifle which had less fixed capital employed upon them ** tho 

 medium in which price was estimated, and that all thnan which had 

 more would positively fall in price when wages rose. On the contrary, 

 if wages fall, ihose oommoditiee only would fall which had a Us* pro- 

 portion of fixed capital employed on them than the medium in which 

 price was estimated ; all those which had more would positively rise 

 in price." 



With all those causes of disturbance in the relations which the 

 different products of labour bear to each other, it is obvious that no 

 commodity can be a perfect standard by which to compare the varia- 

 tions in the value of other commodities ; but as, in an advanced stage 

 of society, labour cannot be the ordinary measure of value, some 

 representative of labour must be selected, by which to carry on the 

 exchanges of trade, and the more nearly it represents the amount of 

 labour expended upon it, and the less that amount varies, the fitter 

 will it be for a common standard of value. 



t The precious metals, or paper convertible into them, ore the 

 standards usually adopted. They ore however articles of commerce 

 varying in supply and demand, and in the quantity of labour required, 

 it ditterent times, to produce them. They cannot therefore bo 

 invariable standards, but must fluctuate more or less like otlu i 

 niodities. Practically, this variation is not, upon the whole, so great 

 as in the case of other articles, but in the degree in which it prevails it 

 makes gold and silver imperfect standards of value. The circum- 

 stances and results of this imperfection and the means of obviating 

 them are among the most important speculations of the political 

 economist, but ore more fitly treated of in other ports of this work. 

 [BANK; BANKI.M:; CUBUKMCY; EXCDA , &.] 



(Adam Smith, MYufrA of Natiant ; liicardo, Principle* of Political 

 Economy and Taxation ; Mill, MemcKlt of Political Economy ; Say, 

 Rirhtut do yalioui.) 



VA1.VASUK. IVAYASOH.] 



VALVK. A moveable partition introduced in machinery for the 

 purpose of alternately opening and closing a passage through which steam 

 or water may be intended to pass, is called a ralve ; and this generic 

 name receives many tpecific designations according to the position, or 

 tho function, the valve may bo required to occupy, or to perform. 

 Thus there are head, or feet valves; suction valves; delivery, dis- 

 charge, air-pump, steam, safety, blow-off valves ; spindle, clack, Hap, 

 slide, cup, crown valves; ttop, expansion, distribution, equilibrium, 

 and countless other varieties of valves, which can only be described in 

 tiio detailed notices of the machinery of which they form part. It 

 may suffice, then, to state here briefly, that the conditions a valve 

 is required to fulfil ore, that it shall open freely in the required 

 direction; that it offer 110 obstruction to tho passage of the fluid it 

 is designed to pass when it is open ; that when it is closed it shall not 

 allow the fluid to return. Volvos must, therefore, fit closely on their 

 seats ; be sufficiently strong to resist the pressure to which they ore to 

 be exposed ; they must be composed of materials which should not be 

 likely to suffer deterioration or wear ; they must be accessible at any 

 time for examination and repair. In the exceptional forms of throttle- 

 valves, tho majority of the last-named conditions apply ; though, of 

 course, as those valves are not intended effectually to close the passage 

 of the fluids they intercept, they do not require the same amount 

 of strength, or the same perfection in tho seating, as the ordinary 

 valves do. 



It follows, from the nature of the work performed %y ordinary 

 valves, that great mechanical perfection is necessary in their execution. 

 The bearing surfaces are, therefore, carefully planed, turned, and fitted ; 

 and the face of the valve itoelf is frequently covered with a emi- 

 clastic material, for the purpose of more effectually excluding the 

 passage of the fluid* ; or it may be kept close against the seating by 

 means of springs. These contrivance*, however, necessarily give rise 

 to considerable friction on the opening and shutting of the valves, and 

 I thence becomes necessary, in designing machinery, to diminish the 

 weight and tho number of the valves as much as possible. Moreover, 

 as valves only open when the pressure on one side exceed* that upon 

 the other, the effort required to open them may become a question 

 of serious importance, and the reaction which may ensue up. 

 using suddenly closed may frequently exercise a powerful oflect upon 

 the solidity of the machinery ; a* for imtance, in the cases of a valve 

 upon the rising main of a large pump, or of the expansion gear of a 

 rttam-cngine. It is for the purpose of obviating these sources of 

 hMasMrisne. and danger, that the cup-valves and the 



. 



valves, before alluded to, under Itm* and STKAM-EXQINK, ar. 

 OHM ; fur ordinary purposes it may be considered that /i/fi-valvos 

 ore adapted for rough work and for diavw fluids; that Ainynf-valvos 

 piwnt some mechanical advantages over the lifting-valves ; and that 

 i. In n there is a necessity for gradually < . .-usage, or for pro- 



venting ;the escape of a rare fluid, the liidiog- valves should be re- 



Flap- valves, and screw-valves, are occasionally used in hjv. 

 Ulnsa liifl : the former, for the purpose of securing an autouomic 

 discharge of drainage water* whenever the internal pressure on tho 

 valve shall exceed the external pressure ; and the Utter, for the purpose 

 of intercepting the flow of water, or even of gas, in pipe*. Keif-acting 

 balance-valves are often used for ventilation, and occasionally for the 

 purpose of regulating the draught in furnaces, chimniea, fto, A wry 

 ingenious system of self -acting balance valves was introduced by .Mr. 

 Thorn in the Urecnock Water Works, to ensure the uniformity of How 

 of the mill streams ha had there to deal with : a full account of these 

 contrivances is to be found in. tho ' Annalus des Pont* et Cbausseos' 

 for 1831. 



VALYL. [BUTYL.] 



VAMl'IKK. According to Dom Calmct's ' Dissertation sur let 

 Vampires,' the vampire is a dead man, who returns in body and soul 

 from the other world, and wander* about the earth, doing every kind 

 of mischief to the living. Generally he sucks the blood of | 

 asleep, and thus causes their death. Those who are destroyed in this 

 way become vampires. The only manner of getting rid of xiu h un- 

 welcome visitors is, according to the same author, to disinter 

 bodies, to pierce them with a stake cut from a green tree, to cut olf 

 their heads, and to burn their hearts. 



The belief that the dead sometimes return to this world, in ori 

 annoy the living, was prevalent in very early times. Eastern n.iticMM 

 have a similar superstition about malicious ghosts, called " gouls," &c. 

 The belief in these apparitions was not destroyed by the introduce ;..u 

 of Christianity, but remained, like many other super.- 

 bequoathed by paganism, in hill force during the middle ages. Tho 

 laws of Charlemagne (' Capitulorium pro 1'artibus Saxonim') c 

 certain enactments respecting apparitions called Striga or Hasoa (this 

 lost word signifies a shapeless being). This circumstance proves tho 

 generality of this belief during that period. 



The advance of civilisation in modern times was unable to destroy 

 a superstition founded upon a feeling by which the great mass of man- 

 kind is so frequently actuated fear ; and many author* wrote books 

 on the subject. Besides Dom Calraet, whom we have quoted, we may 

 mention Philip Herius, on author of the ITth cuit'iry: W 

 Kau ft, who published in the last century a treatise ' De Masticatiouo 

 Hortuorum in Tumulis ;' Ferdinand von Scherz, ' In Magia I'osthuiua,' 

 Olmiitz, 1706, &c. 



The superstition about the vampires is chiefly prevalent in soma 

 parts of Eastern Europe. These apparitions ore known in i 

 under the name of " Upior ;" in the Ukraine, " Upeer ;" in Russia, 

 " Googooka ;" in Hungary, Servia, Greece, Ac., " Yroucolackas," 

 * Vardoulacka," " Broncolucka," Ac. 



Of all those countries, Hungary and its dependencies may be con- 

 sidered as the principal seat of vampirism, and little more than a 

 century bos elapsed since all Europe was filled with reports about tho 

 exploits of vampires in Hungary and Servia, It was during the five 

 years from 1 730 to 1735 that vampirism reached its height. It was 

 so general, that Louis XV. of France commissioned his ambassador 

 at Vienna, the Duo de Richelieu, personally to ascertain, in Hungary 

 and other Austrian dominions, the reality of vampirism. The French 

 diplomatist denied in his report to the king the existence of tho 

 vampire*, and he informed him at the same time that the anccdotea 

 about them were inserted in the contemporary records of tho Austrian 

 tribunals. This superstition gained ground so much that tho chief 

 periodicals of that time contain accounts of cases of vampirism in 

 Hungary ; such as, for instance, the ' Mercure Historique et 1'olit i< |uc,' 

 for October, 1736, pp. 403, 411 ; and the Dutch paper, ' Le Glaneur,' 

 No. ix., for 1733. 



A great number of anecdotes, many of which had been officially 

 registered, ore related by contemporary writers ; some of them i v, 11 

 described the manners and customs of those vampires ; as for instance, 

 that lying in their graves they suck and chew their winding-sheets, 

 and that it was therefore necessary to place under their chins n 

 of green turf in order that they might not be able to reach the sheets 

 with their teeth, and to bind their hands, that they might not turn 

 about in their coffins. Many believe that tho vampires, notwithstand- 

 ing all the means used to destroy their bodies, will resume their shape, 

 and recommence their mischievous wanderings as soon as the rays 

 of moonlight foil on their graves. This superstition is chiefly pre- 

 valent in Greece, and the tale of 'The Vampire,' written by Dr. 

 Polidori, was founded upon it. 



It may be supposed that the superstition about the vampire has 

 derived considerable strength from cases where men, supposed to be 

 dead, have been buried alive. Such cases have happened in many 

 countries, as has been shown by the altered position of the body in 

 the coffin, spots of blood on tho torn winding-sheets, bites on thu 

 hands, and other marks of the struggle and despair before life became 

 extinct It is probable that such signs have beeu sometimes interpre- 

 ted as the marks of vain- 



VANADIC ACID. [ VAKADIVM.] 



VANADIUM (V). A rare metal. It was dincovored in 1801 b/ 

 Del Hio, and in 1S30 named, by Sefstrom, Vanadium, from 

 cognomen of the Scandinavian goddess fr'rtiti. In exceedingly miUute 



