I s o 



fimpte. Pifl. Gormens feveral, ovate or oblong, fiipenof, 

 feilile. ftyles fimple, fcarccly fo long as the gcrmens ; ftig- 

 mas obtufe. Paic. Capfulcs feveral, foliile, leguminous, 

 oblong, of one cell and one valve, keeled at the outfide, 

 burfting at the inner edge. Steils numerous, attached in 

 two rows to the edge of the capfule. 



Eli". Ch. Calyx n»ne. Petals five, deciduous. NeiTla- 

 ries tubular, three-cleft. Capfules felfile, of one cell and 

 one Valve. Seetls numerous, marginal. 



1. \. fumarioides. Linn. Sp. PI. 783. (Helleborus fu- 

 warix foliis ; Ammann. Ruth. 74. t. 12.)— Stipulas awl- 

 frtaped. Leaflets pinnatifid. Capfules nearly cylindrical. — 

 Native of moill (hady places, near rivers, in Siberia, flower- 

 ing in fprirg and fummer. It is fometimes cultivated in 

 gardens, as being not only curious, but an elegant little 

 a'jnual plant, with the habit and glaucous hue of a Fmnarln, 

 to feveral of which genus its leaves bear a great refen.blance, 

 in tht-ir pinnatiiid obovate leaflets. The Jl-jivers, however, 

 are totally different, refembling a Thaliarv.m, fmall, whitifli, 

 fl'.ort-lived, on long fimple lldks. Capfules about ten or 

 fifteen, fpreading, pale green, near half an inch long, 

 pointed with the permanent ftyles. 



2. I. thaliarol-ks. Linn. Sp. PI. 783. Jacq. Auflr. 

 t. 105.— Stipulas ovate. Leaflets three-cleft, dilated. Cap- 

 f;iles ovate. — Native of fliady rather moift places, in the 

 tnountains of Italy, Carnioja, Auftria, &c. flowering in 

 April and May, and foon ripening its feed. Root creep- 

 ing, perennial. Stem a fpan high or more, naked below, 



■fmooth. Leaves temate, leaflets more or lefs three-cleft, 

 ■broadifli, fmooth, refembling thofe of an ylqulkgia, or Tha- 

 iiSnim. Flotuers white, with yellow ftamens, not unlike 

 lomtiXmsW Anemone. Cap/uLs only tfm or three, ovate, on 

 a globular receptacle. 



Such are the only certain fpecies. I. aqti'th-gmiles of 

 Linnaeus appears to be ?, nonentity, its fynonyms, as far as 

 they can be mtide out, belonging to jlquilegia ■vifcofii, w hich 

 is K;iller's If.pyrum, n. 1 190. 



Mr. Sahibury, in Tr. of Linn. Soc. v. 8. .^oj, has 

 ©•lablifiied, by the name of Coptis, a very natural genus, 

 though diflingnifUcd from Ifopyrum chiefly by having ftallced 

 germens and capfules. Of tiiis ore fptcies is IhHehorus tii- 

 fo'lius of Linnreus, Fl. Dan. t. 566; the other is C. ajj)!e- 

 nlfolii of Salifbury, of which we have fpecimens and a draw- 

 ing from Mr. Menzies, who gathered the plant on the weft 

 coad of North America. This lafl, ftrange to tell ! ap- 

 pears, by fpecimens from Thunberg, to be liib Tha/ielnimjti- 

 jiortieiim, Tr. of Linn. Soc. v. 2. 337, called in FL.Iap. 364. 

 Didjnaml/la Salvia: Jiniilis, though nothing can be kfs luit- 

 able than the latcer defcription. He informs us he had 

 never feen the flower, only the fruit. 



ISORA, a Malabar name for fome fpecies of the He- 

 Uteres of Lirn ens, and adopted by Plumier to deiignale 

 that genus. Sec Helicteres. 



ISOSCELES TlUAVGLE.of «7o.:, equaJ,zn6.^y.^\'>.;leg, is 

 a triangle wliich has two equal fides. In an ifofceles triangle, 

 FDE ■.PlateVlll. Geometry, fg. IOC.) the angles jr and «, 

 oppofite to tlic equal fides, are equal: and a line drawn 

 from tlie top or vertex F, cutting the bafe into two equal 

 parts, is perpendicular to the bafe. The fa.me line alfo 

 .bifects the vertical angle of the triangle. It appears like- 

 wife that if the equal fides be produced, the angles under 

 the bafe will be equal, the fum of thofe above and below 

 refpectively being equal to two right angles. And if the 

 vertical angles of two ifofceles triangles be equal, the two 

 triangles will be equiangular. Moreover, every equilateral 

 •tFiwgie ntuit be eqiiiangubr. 



I S P 



ISOTONIC Scale of Mufc, or the Equal Tem- 

 perament Scale, is that in which the oftavc is divided 

 into twelve equal parts ; of courfe, each half note is equal 

 I H- '4^2 = 51 £ 4-/4- 4rS-w, which is fometimes called 

 a mean femitone, and tliis, a fyllem of mean femitones. The 

 following table flicws fome of the moil ufeful particulars ot 

 this fyflein, -j/=. 



The laft column of this table was publifiied in tike 

 Philofophical Magay.ine, vol. xxix. p. 347 ; in the xxxyitli 

 vol. p. 47, fchol. 7, the temperaments of the concords 

 in this fyilem will be found, and in vwl. xxxv. p. 452» 

 he beats of all the concords. Broadwood and fome 

 other tuners of pianofortes pretend, it is faid, that 

 they tune them to an equal temperament, but which ii; 

 very much to be doubted. On the organ, it feems clear, ap 

 Mr. Smyth obferves in the Phil. Mag. vol. xxxvi. p. 435, 

 tliat an equal temperament never has been, and we may per- 

 haps fay, never will he praflifed : however many advocates 

 this fyflcm may have had among fpeculative writers, among 

 whom have been mentioned D'Alembert, Cav;i!lo, Chladiii, 

 Couperin, Davis, Des Cartes, Emerfon, Marpurg, Merrick, 

 Merfennus, Rameau, Ricci, &c. Mr. Farey, 1:1 propofintr- 

 what he calls his equal temperament, in the Phil. Mag. vol- 

 xxviii. p. G^, exprefsly ftated his objeiS to be, to enable thofe 

 to tune it who might wifli to try it, and not as recommending 

 its adoption. See Equal Tk.mpeuament. 



ISPAHAN, in Geography, the capital city of modem 

 Perfia, fituated in the province of Irak, on the fmall river 

 Zenderud, which rifes in the mountains of Galabat, three 

 days' journey towards the north ; but Abas the Great, at a 

 prodigious expencc, pierced fome mountains about 30 leagues 

 from Ifpahan, and introduced another flream, fo that the 

 Zenderud was as large during the fpring, as the Seine at 

 Paris in the winter ; for, in that feafon, the fnows on the 

 high range of mountains melted, and very much fwelled the 

 river. The city is furrounded by walls of earth, which are 

 fuffered to remain in bad repair, and which are concealed by 

 the adjoining houfos and gardens. It has eight gates, which, 

 according to Chardin, could not be fluit ; and its flreets are 

 nan-ow, devious, and badly paved. This writer compute.? 

 its circuit, the fuburbs intlud'.d, at about 24 miles, and its 

 inhabitants, by the lowelt elHma'e, at 600,000. But the 

 royal fquare, or Meidan Sliah, and its grand market, the 

 palace of the Sefi, and thofe of the grandees, the mofques, 

 the public bath, and other edifices, are magnificent and 

 fulendid. Its canals, the plantations of loftv plane trees on 

 ; R ^ ' botk 



