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.?7 ! 5 ^ R . eiE 711 * &£ ihflafnmable materials ^ that the fuperincumbent bafak or waoke is melted by this heart,-’-and i! fl©W6 into thefe hollows ; and that water rufhes in- oft thft'iforface of this melted mafs, -and occaflon* its expMfion. *v vX'Vv . ..tsv u\> -.^w? •jA's CoA’i? i^Hence the conditions for the exiftehceVof 'a vol cano appear to be \the .following A i. Afubftanoe capable iof combuftion ♦, and this" we -thay fairly infer to be coal: 2. Adtual cbni boll ion,w.whioh ■may:be caufedc by theufpontaneous inflammation of the coal,) or.iitsrbEing!kindledi by lightning? 3. The melting of the ftony bads that reft r on* the coal :h4. The .riAIngin: of • water fromthefea^ or from the furface of the land during wet.feafons, -or ibyi'the flawing ^hi I of rfmall-rivers cd Hakes: •$; The'prefence of a power capable of forcing the (jtielted'matter frhtn its bapbfltohy j andiicdiTsi we may conclude to be aqueous vapour. sdJ isbHnoo .0 >iv*ii. <p.H IcioniM ir.Imifii; c I ' I, By mineral.repertories, we-underftand thofe Spaces that contain the various mineral fubjlances of which y.vvi’A—tmbiidtail CHAP. XI ' vi ■''' y'lnccr llltfERAL REPOSITORIES., Lagerstatte.—W erner. t f»;;3