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about Newcastle and Durham call it plate. The stratum of this isabout a yard thick, lying 120 feet deep, and 30 feet above theCanel-coal. One specimen he describes as a black slaty coal,marked in a quincunx manner, &c. much like what might haveproceeded from the bark of common fir. Another he describesas having the appearance of long striated leaves, having the ap-pearance of joints, &c. upon a dark grey slaty stone. The stra-tum of this, he says, lay at the depth of 25 fathoms, in Bransty-cliff, by the Duke of Somerset's salt-pans, near Whitehaven . Thestratum, he says, was about a foot and a half thick; and upon thebreaking of the stone, leaves of plants appeared very thick in all partsof it, where the grain of the stone was thus fine and dense. Butwhere it happened to be more gritty, coarse, and lax, there was notone leaf to be met with *. Specimens of schisti thus bearing impres-sions of vegetables are displayed Plate I. Fig. 6. and 7*; Plate IV.Fig. 6. and 7-; and Plate V. Fig. 1, 2, 3, 6, 7» 8, 9«
The impressions of leaves are much more rarely discovered in thesand-stone strata, and are traced with much more difficulty; owingin part to the uncertain direction, in which these stones often split;and, in part, to the leaves being twisted, and to their laying in aconfused and irregular direction : hence the leaf is generally dividedwith the stone, and its edge, or section, only exposed. Sometimes,however, a very fair impression of a leaf may be seen, on sand-stone ; but it will be found, in general, to differ very much in somerespects from the impressions on the argillaceous schists. Plate V.Fig. 4. and Plate III. Fig. 3, 4, and 5. represent the impression ofvegetables on different kinds of sand-stone.
The occurrence of vegetable remains in lime-stone strata is un-doubtedly much more rare than in the argillaceous, or schisti.Schultzen suspects some error in those accounts which state their