■■ Ihfcrt'ptm of fomrneio Fo/Jtts. 213 



muriatic acid it is infoluble. With very concentrated fulphuric acid it flrongly effervcfces, 

 emitting then whlteifh, gafeous vapours, which attack glafs. This peculiar foffil confitts 

 of alumine, fluoric acid, and' a little pot-a(h. It occurs in Greenlaod>. but its^ native .par> 



jicular fpot is not yet known, though it appears to form ftrata. '.'■'< - ''l'-;;-!i': j,,;(.-. 



'"' ■.' ' :! 01 '{"KI '-id 



XII. SCAPOLITE. 



The colour of this ftone is yellowifh and greyifli-White, and alfo fmoky-grey. Its ex- 

 ternal luftre vitreous, from the glofs of wax to a brighter polifti, but its internal luftrc has 

 little brillliancy. This ftone is piore.or Icfs tranfparent on the edges, b'ut it is entirely 

 opaque when decayed. Specific gravity from 3..<58oto 3.780. It admits of beijig ifcratched 

 with a knife, but itfelf fcratches glafs. Its ftreak is whife. The cryftals are nearly 

 re£langular quadrilateral columns (having angles from 85° to 95°), with very flightly trun- 

 cated lateral edges, without pointed terminations. Thefe cvyftals are very minute, and irr 

 that cafe alnioft needle-fliaped ; feldoni large,, with tranfverfe Oiootings,- and longitudinally 

 ftriated. The fmall and very fm'all ones are ufually concreted crofs ways with each other 

 In regular chillers (dyufm) and prjfmatic ; but the larger are totally, bedded in the matrix. 

 Their t.exture is Jamellar, but in the larger cryftals ,it approaches to the ftriated. When 

 fplit a vifible diagonal crofiirig'is percei'ved lengthways, and a fecond piie lefs perceptible 

 which is longitudinal and oblique-angular. The crofs fra£l:ure of fcapolife is uneven, and* 

 the fragments of this fra£lure are pnfmatic (bar-like). It may be eafily'broken, and" is- 

 not ele£tric. Before the blow-pipe it readily fufes, with frothing. Into a white re- 

 fplenden't enamel. It is found in the iron-iniries riear Ar.endal> iiV Nbrwar; 



iir. 



. . i t:.! v<j ii;) r-)5ii' •- . :c.i ; i ;. 1 Jli/.'Ji. ' , 



EifetiiUkti '^t^hpkjdtmni In the Properties of Wind In0uine':Air, confyllng of- ttfinglt Pipt 

 or Chaiitid ; lu'iih Improveih'ent's iti iheiV ConJtriiElioh. By Mr. Wtti. V/iM Cwst. ■ ■ * 



r. Tpi W5r. iNICHOLSQN. , , 



SIR, 



O'.J; 1;,: \.\y. - : i.: \i: .\ .-.-^ \ : t- Y, Vil.-(: /; ,i in;: /idM! , j ') ;.-i : !:j: ^;; . : ' 

 N every .•vi^indii^ftrument of mupCj, which has-fhe, intervals j,ofijs fcale regulated by 

 holes for the fingers of the n^ufician, ;itia impracticable, to^tranfpofe the keyt of an air half a 

 toijei witl|ou.t altogether changing the mode. of fingering.' -If ,no alteration can be made in 

 the length of the inftrument, to perform a quick fucceffion of chromatic, intervals is npt 

 cafy; but when fome of the chromatic notes are alTumed for the key of an air, the fingering 

 is attended with fo many difBculties, that the melody can only be well executed by a per- 

 former of tranfcendent abilities. 



The. 



