Wood partly petrified by Carbonate of Lime. 213 



Further Notice on the partially petrified piece of Wood from an Ancient 

 Roman Aqueduct in the Principality of Lippe Buckeberg. 



[Read December 14, 1836.] 



Since I communicated to the Geological Society, the preceding notice on 

 the partly petrified wood from the ancient Roman aqueduct at Eilsen, in the 

 principality of Lippe Buckeberg, Mr. Robert Brown has shown to me a speci- 

 men 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 aqueduct, 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 inclosed within and sur- 

 rounded by the unchanged wood. See PI. 16, fig. 3. 



Mr. Brown has observed another remarkable circumstance 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 magnified engraving, PI. 16, 

 fig. 4. 



From this it appears, that the petrifying process had not been so fully com- 

 pleted, as in the portion of the same wood, which first came into my possession ; 

 but on referring to that specimen, I have found some instances, in which a 

 part of the medullary ray, that passes through the petrified portion, has not 

 been so completely changed as the surrounding longitudinal fibres, or the part 

 of the same ray, which is more in the centre of the petrified portion. 



Of the rest of this specimen, some part is much decayed and worm-eaten, 

 while another part is hard and in good condition; and the line of separation 

 between them, is, in some places, remarkably well defined. 



Although the latter does not to the eye, present any appearance but that 

 of sound wood, I was induced to examine it, and had the pleasure of finding, 

 that, what may perhaps be considered as the first stage of petrifaction, has 

 taken place in it. 



I cut in a transverse direction as thin a piece as I could detach with a sharp 

 knife, and placed it in water under the microscope, then adding with the 

 point of a quill a drop of muriatic acid, I immediately perceived the disen- 

 g-agement of gas, which seemed to proceed chiefly from the inside of the 

 larger vessels, as if an extremely thin coating of carbonate of lime had been 

 deposited within them. In the more decayed part, there is also a slight action 

 produced by the acid, but not so strong as in the sounder part. 



