[ 12 ] leaves, mutl be called micaceous ftones, or mica: j daze, or glift, in Englifh. * 26. There are a great many ftones, which, at the very firft appearance, are compounded ones. It is impoftible to devife a Ihort and eafy method for affaying them in this general and fummary way. Stones and earths which are homogeneous, or nearly fo, are beft fuited for experiments. Thofe that are confefledly compofed of particles of one, two, three, and more earthy or ftony fubftances, if their particles be flinty only and fmall, they are fand-ftone; if calcareous, and compofed of round grains, they are fpawn-ftone; if large, and of a flinty nature, glued as it were to gether, they are pudding-ftones; if the inte grant parts be of more than one kind, thev are rock-ftoncs (karn, or moor-Jlones) ; to which kind the granites and porphyries likewife be long, being really of the fame nature, only of a finer texture. 27. If the earths or ftones have a configuration bearing a great fimilarity to fome of the ani mal or vegetable fubftances, they are petre- faftions; which may be divided into real petrefaffions, into in cruft ations, into imprejfions, and lufus nature; according as the animal or vegetable fubftance is either really changed into itone ; or has been only covered or coated with a layer of ftony fubftance; or has only made an imprefllon on the ftony fubftance- before its induration ; or if the ftone has only an accidental fimilarity with an animal or vegetable, or parts thereof. S E C-