G R A 



GRAPHICAL Perspectivk, in Ophcs, is an inftrument 

 defcribi.-a by Mr. Martin, conlilliiig of a tube containing 

 two convex knfes, whicl; arc placed at twice their focal dif- 

 tance from each other ; and in their common focus is another 

 glafs, divided into equ:d parts witli the point of a diamond. 

 'J'hough this iii'irument does not magnify any object, yet 

 the angle \inder which an objeA is feen is eafily known by 

 it ; and lu.ce this angle varies with the diftance of objeAs, it 

 is eai'ily applied to the purpofe of meafiiring inacccflible 

 lielghts and dillances ; and ilnce the field of view is divided 

 into equal fquares, it is ufeful in drawing the perlpeftive 

 appearance or objecls. Moreover, as all foreign light is ex- 

 cluded by the tube in which thefe lenfes are incloied, pic- 

 tures feen through it have a fine relievo, on which account, 

 and alio bccaufe objects appear inverted through it, the 

 images of a camera obfcura are viewed with it to peculiar ad- 

 vanta-re. If a lens of a greater focal length be fixed at a 

 prop °r dlftanco from the centre of the tube, this inif rument 

 will be a telefcope, and will magnify the prints which are 

 looked at through it ; and if a fmall lens be ufed, it will be 

 a microfcope, and the fame micrometer will ferve for them 

 both. Martin's Optics, cliap. xvii. p. 280, &c. 



GRx\PHIDA, in Natural H'ljlory, a name by which fome 

 authors have called the mcrochthus, or French chalk. 



GRAPH IS, in Botany, from y^x^-x, to write, a name in- 

 vented by Adanfon, who is pleafed to fpell it gmjis, and 

 adopted by Ehrhart, for the various fpecies comprehended 

 under the Lichen fcriptus of Linnasus, and which conllitute 

 the very diftinft genus of Opegrapha in Acharius; fee Eng. 

 Bot. v. 25, 26. t. 1753, &c. 



GRAPHISCUS, in the Writings of the Ancients, a name 

 given to an inftrument ufed for extracting darts from wounds. 

 It is faid to have been the invention of Diodes, and is de- 

 fcribed by Celfus. 



GRAPHITE. See Plumb.\go. 



GRAPHOIDES, -/p.?ioeJ.r, in Anatomy, an appendage 

 of the bones of the temples, long, fmall, (harp, and a little 

 crooked, like a cock's fpur ; called 3.UoJIy hides. 



The fame name is fometimes alfo applied to the mufculus 

 d'gaftricus. 



Likewife to an extcnfion of the brain, refembhng a writ- 

 ing pen. 



GRAPHOMETER, a name which fome authors, par- 

 ticularly the French, give to a furveying inftrument, by us 

 commonly called a /fw;V;;r/f ; which fee. Mr. Nicholfon, in 

 the fifth volume of his '• Journal,'' 8vo. has defcribed, and 

 tUuftrated by appropriate figures, a fubterranean grapho- 

 met^r, invented by M. Komarzown<i, F. R. S. and pre- 

 fent.;d to the National Inftitute of France. It is a fimple 

 conftruction of the common theodolite (which fee), and is 

 calculated to a.ifwer the author's intentions in operations 

 like thofe of mining, where great accuracy is net required. 

 In vol. i. of the fame "Journal,'' we have the deicription 

 of an inftrument refembling a graphometer, invented by 

 Cit. Caranfeau, for determining the mutual inclination of 

 the faces of a cryltal, or its prominent angles ; it confifts 

 of two concentric, equal quadrantal arcs joined by a hinge ; 

 to which are applied compafs-legs or radii, capable of 

 being fliortened to apply to fmall cryftals, &;c. See Go- 

 KlOitETiin. See alfo /"tof VI. Cry/l/illography,fig.r)^. 



GRAPNEL, or Gkai'LING, on Ship-boanI, a kind of 

 fmall anchor for boats or gallies to ride by. It differs from 

 other anchors, as having four or five flukes and no fnack, 

 though there are fome witli th.ree flukes, with which they 

 ufe to fweep for havvfcrs or fmall cables. In men of war 

 alfo, the grapnels, or at lead a lighter kind of them, whofc 



G R A 



flukes are furnif.ied with ftrong barbs on their points, arr 

 uled to be thrown into an enemy's fhip, in order to catch 

 hold of fome of her gratings, rails, gun-wales, &c. this is 

 done in order to boardirg of her. They are particularlv 

 ufeful in nre-fliips, and cnlled firc-grapplings. 



GRAPPLE, in the Manege. A horfe is faid to grap- 

 ple with one or both legs, wh?n he catches or raifes them 

 more haftily and higlier than ordinary, as if he were cur. 

 vetting. 



G RAPTOLITHT, in Natural Hi/lory, are the petrificata 

 fifta of LinnsEUS and others ; as dendrita-, landfcape -marble, 

 dcndropotamiles, Sec. al! wh;ch, acconling to Mr. William 

 Martin, " Outlines,'' p. 8. Ihould be excluded from the 

 lift of extraneous follils. 



GRASS, GiiAMKN, in Botany, See Gramina. 



To enumerate all the fpec''S of grafs which are found 

 growing naturally in England, would greatly e.vceed the 

 bounds which can be allowed for this article ; it will fuffice, 

 tlierefore, to mention a few fpecies, which are either ufed in 

 medicine, or cultivated as a pabulum for cattle ; for there 

 is fcavcely a pafiure in tliis country where great numbers 

 of diflerent fpecies are not to be found intermixed. Mr. 

 Rav has ranged them in the following order, 172. wheat- 

 erafs, rye-grafs, darnel-grafs, panick-grafs, canary-grafs, 

 fox-tail grafs, cat's-tail grafs, hedge -hog grafs, crefted. 

 grafs, oat-grals, cock's-foot-grafs, buck-grafs, and millet- 

 grafs. Thele and other graffes Linnxus has arranged into 

 diftinct genera. See the following articles : 



Gra.s.s, Arroiv-headed. See Triglochix. 



Gras.s, Bent. See Agho.stis. 



Gr.\.s.s, Bird. See BlRD-^r^. 



Gha.s.s, Canary. See Piial.vris. 



Ghas.s, Capon's -I ail. See Fe.stl'CA, 



GltA.s.s, Cat's-tail. See Phleu.m. 



Gr.\.ss, Clover. See Trefoii.. 



Gr.\.s.s, Ccck's-tail. See Dactyli.s. 



Gras.s, Cotton, See Eriophorum, 



Gra.ss, Couch. See Triticum. 



Gra.s.s, Crejled. See DoG's-/i;;/-^ri7/}.and Cvno.<>x'rt;.s. 



Gr.vs.s, Dog's. See Triticum and Agrosti.^. 



Gr.v.ss, Sea-dog's, a name fometimes given to the double 

 fpiked fccale, or rye. See Secale. 



Gra.ss, Dog's-tail. See Doo' i-tail-gra/s and Cyxo.SURUS, 



Grass, FeJ'cue. See Festuca. 



Grass, Fo.v-tail. See Alopecurus. 



Gra.ss, Goofe. See Asperuoo. 



Grass, Hair. See AlRA. 



Grass, Hare's-lail. See Lagurus. 



Gr.Vss, Knot. Sec PoLYGONU.M. 



Gr.ass, Knot, German. See SrLEU.WTllfS, 



Grass, Knot, Mountaitt, and Verlicillate. See liLE* 



CEIIRU.M. 



Grass, Love, or Quahng. See Brij^.v. 

 Grass, Meadniv. See PoA. 

 Gra.ss, Hard meadoiv. See Cvnoslrus. 

 Grass, Millet. See MiLR-.M. 



Grass, Oat, a name given to a fpecies of the feftuca. 

 See alfo A\"KN.\. 



Gr.\.ss, Panic. See P.^nklm. 



Gr.\s.s of Parnajfm. See Parn'A.^sia. 



Gr.\ss, Pepper. See Pii.VLARl.v. 



Gr.\ss, Pudding. See Mentha. 



Gra.s.s, Quaking. Sec Briza. 



Gra.ss, Rattle. Sec Pedicularis. 



Gha.ss, Rujh. See S( iRPL.s. 



Grass, Rye, or Ray. See Loliu.m and Hordkum. 



Gr.\ss, Scorpion. See Scorpiukus. 



Gras.";^ 



