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 720 SHORT CONTRIBUTIONS TO VARIOUS WORKS,

forms me that all the wood he found is coniferous." Gcol. Trans., 2nd ser., vol. iv, p. 474 (1836).

Mr. Charles Stokes in his " Notice respecting a piece of Recent Wood partly petrified by Carbonate of Lime" {Trans. Geol. Soc. of London, 2nd series, vol.v, p. 207, 1 840), acknowledges assistance obtained from Mr. Brown, and in a "Further Notice" appended to this paper (1. c, p. 213) he says —

" Since I communicated to the Geological Society the preceding notice on the partly petrified wood from the ancient Roman aqueduct of Eilsen, in the principality of Lippe Buckeberg, Mr. Robert Brown has shown to me a specimen from the same piece of wood, which was presented to him at Tharand, in the month of October last, by M. Cotta of that place, who discovered the wood in the aque- duct, and remarked its peculiar condition. Mr. Brown has pointed out to me, in the longitudinal section, that the petrified portions, in his specimen, are about two inches in length, and in the middle part, nearly a quarter of an inch in diameter, and terminate in a point at each end. The petrified portions are, in these instances, completely enclosed within and surrounded by the unchanged wood. See pi. xvi. fig. 3."

"Mr. Brown has observed another remarkable circum- stance in the condition of these petrified portions. The change of the longitudinal fibres appears to be complete, but the medullary rays, of which the ends are seen in this section are still in their ligneous state, as shown in the mag- nified engraving, pi. xvi, fig. 4."

Dr. Fitton, in his paper " On the Strata below the Chalk," says —

" From the evidence afforded by thin transparent slices, both of the transverse and longitudinal sections which have been examined under the microscope by Mr. Brown, the fossil trunks of Portland are found to possess the characters uniformly belonging to coniferous wood ; but it must be observed that these characters are not absolutely confined

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