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VERNI, in Geography, a town of the republic of Lucca ; 

 12 mik-s N. of Lucca. „ „ 



VERNIA, in Ancient Geography, a name which bulta- 

 thius gives to one of the Britift illes, fuppofed by Ortehus 

 to have been Hibernia. „ , , t c ^ 



■ VERNICIA, in Botany, fo called by Loureiro, trom 

 ^,erms, varnirti, becaufe the nuts of this tree afford by pret- 

 furea kind of oily varnifn, either ufed by .tfelf to proteft 

 wood from the weather, or employed to f d"'f ^f/'^Vr r! 

 Chinefe or Japan varnilh.-Loureir. Cochmch. 5S6^Llals 

 and order, Monoecia Monadelphia. , Nat. Ord. Tncocct, 



Linn. Euphorbia, JufT. . , . j j „iv 



Gen. Ch Male, Cnl. Periaoth tubular, m two rounded, eredt 

 fegments. Cor. bell-fliaped, of five oblong fpreading petals, 

 longer than the calyx. Stam. Filaments ten, combmed at the 

 bafe, the inner ones longeft ; anthers as many, arrow-fliaped. 

 Female flowers few, on the fame branch, Ca. and C«r. 

 unobferved. P^/?. Germcn fuperior, roundifli, three-lobed ; 

 ftyle none ; ftigma obtufe, three-cleft. Pmr. Drupa round- 

 ifli, warty. Seed. Nut bony, bluntly triangular, rugged, ot 

 three cells, with an ovate-oblong kernel in each. 



Eir. Ch. Male, Calyx two-lobed. Petals five. Stamens 

 ten. -Female, Calyx .... Corolla . . . . St.gma obtufe, 

 three-cleft. Drupa warty, with a triangular tln-ee celled nut. 

 I. V. montana. Cay deau fon, of the Coch.nchinefe. 

 Tone x6, of the Chinefc.-Native of mountainous woods in 

 Cochinchina, as well as in China. A large tree with amend- 

 ing branches. Lea.es fcattered ftalked, fl.ghtly heart- 



fliaped, pointed, entire, undulated, f'J'°<^;V.P"r/'" J/i 

 two glands at the infertion of the jootjlalk. Fh-^'er-Jialks 

 terminal, many-flowered, (hort. Flo'wers ^^t. 



The wood IS of little ufe for building. The nuts afford 

 a copious expreffed oil, which is yellow, vifcid, tranfparent 

 moderately liquid, ufed as a fort of varmili for arrows, and 

 any wood expofed to the weather. It alfo ferves to increafe 

 the bulk of the far more valuable Chinele varni h, obtained 

 from the Augia of Loureiro ; as well as to render that lub- 

 ftance more fluid and manageable. For lamps it is "Mel^, be- 

 caufe it burns too fiercely and confumes too fpeedily— We 

 have not been able to reduce tliis plant to any known genus. 

 All our knowledge refpeding it is derived f/om Loureiro 



VERNIER, is a graduated index which lubdivides the 

 fmalleft divifions on any ftraight or circular fcale, in the 

 reading of which greater accuracy is reqmred, than can be 

 obtained by fimple eftimation of a fradional part, as indi- 

 cated by a pointer, or fiducial edge. The vernier vvas hril 

 invented by Pierre Vernier of Franche Comte, and made 

 known to the world at Bruxclles {or Brufl-els) in the year 

 1 6? I, through the medium of a pamphlet entitled l.a Uon- 

 ftruftion, I'Ufage, ttles Proprietes du Quadrant nouveau dc 

 Mathematique," &c. Itfoon gained the preference over the 

 fcale of Nonius, which was a circular diagonal fcale, and 

 which by fome writers is yet confounded with a Vernier s 

 index, though there is no greater refemblance between the 

 two, than exifts between the dial of a clock and the hand 

 that points to it. The vernier is applicable to any ftraight 

 or circular line, provided the divifions be equal ; but the con- 

 trivance of Nonius was in the graduated line or fcale itlelt, 

 and required the aid of a fiducial edge as an index. We 

 have (riven the reprefentation of a wrm^r in feveral ot our 

 aftronomical plates, when we were defcribing CnuMC, 

 Equatorial, QuADHANT,TKANsiT-/,^r»mc«/, and 1 iiKO- 

 DOLITE, therefore it will not be neceiTary to introduce any 

 other figure for the purpofe of lUuitrat.on ; particularly 

 as X.\^e principle of its application can be made clearly intel- 

 ligible by cither arithmetical or algebraical notation. Let 

 us fuppofe two lines, either ftraight or portions of circles, to 



V E R 



be exatlly alike in dimeniions, one called A, and the other B, 

 and let one of them be divided into more equal parts than the 

 other by unity ; then will the difference of any two of the 

 equal parts of the two lines, or arcs refpeaively, be a frac- 

 tion, the numerator of which is the common length of the 

 equal lines, or arcs, and the denominator the produd of the 

 numbers of parts into which each is divided. For if we 

 put A for the common length of the equal lines, or arcs, 

 with « and n -f- I for the equal parts into which each is 

 divided refpeftivcly, the length of the divifions of each will 



be — and 



n + 1 



and their difference — — 

 n 



n -H I 



A 



n X n + 1 



To exemplify this principle in an arc of fmall radius, let 

 each degree be divided by an engine into three parts, of 

 each 2o', and let it be required that the vernier fliall read to 

 the accuracy of one minute ; in this cafe the fhort fcale of 

 the vernier muft be divided into 20 parts, and,the equal arc 

 on the hmb of the inftrument either into 21 or 19 parts, fo 

 that the diff'erence of the two equal arcs, in divifions, may 

 be = I ; if 21, the former number, is adopted, the reading 

 will be in a backward diredion ; but if the latter {-viz. 1 9), 

 it will be forward ; let the arc on the hmb be 6° 20', and let 

 each degree be divided into three parts, of 20' each ; alfo let 

 19 be the number of fuch parts or divifions; and let the 

 equal arc on the vernier be divided into 20 equal parts ; 

 then n = 19, and « -t- I = 20 will make a difl'erence be- 

 tween a fingle divifion of the limb, and one of the vernier 



_ ^°^°' = ^ = i', as was required. This dijerence 



19 X 20 380 

 becomes the index for fubdividing the fmalleft divided fpace 

 of the limb, and it is afcertained how often it muii: be taken, 

 by infpcdling the place on the divided vernier, where a ftroke 

 oil it exaaiy coincides with a dividing ftroke on the divided 

 limb of the inftrument ; for inftance, if the zero, or ftroke 

 marked o, be the coincident one, the reading may be had 

 from the divifions of the limb only, without any addition 

 from the vernier ; but if the coincidence happens at any 

 other place, fay at ftroke 5, ftroke 8, or ilrokc 10, as num- 

 bered on the vernier, then 5', or 8', or lo', as the cafe may 

 be, muft be added, as the meafure of a fraa.onal part of a 

 divifion, to the meafure read from the divifions only, that 

 are contained between zero on the lim.b and zero on the 

 vernier: the difl'erence, which we have faid is = l' when 

 taken once, is 5' when taken five times, and 8' when taken 

 eight times ; and as the point of coincidence can never be 

 miftaken, wherever it may fall, it will always determine how 

 many minutes muft be added for the fradtional portion of a 

 divifion, that zero of the vernier has advanced into an entire 

 divifion ; and as the eye will form a rough judgment at once, 

 whether zero of the vernier is near ^, -J, \, j, or j ot a Ipace 

 on the limb, this notice will at once guide the cbiervcr 

 to that part of the vernier's fcale, where the coincideiKe 

 will be immediately found ; for as zero of the vernier ad- 

 vanccs in any divifion of the limb, by the flow motion of the 

 taneent-fcrew of any inftrument, the point of coincidence 

 of the ftrokes of the two arcs advances with it. till the ftroke 

 at zero becomes itfelf coincident with a new dividing ftroke 

 of the arc on the limb, which coincidence denotes the addi- 

 tion of another 20', in onr example, without reference to the 

 vernier: but ftiould there be any doubt about the exaai ti.de 

 of the coincidence, 20". 30", "r 40". -^ay be taken mftead 

 of the laft minute, accordingly as the eye can bcft indge^^ 



