slices are naturally prepared, and in the most perfect manner possible.
"Each fibre tapers at both ends to a blunt point, is irregularly four-angular, and solid throughout, its cavity being filled with transparent silica, and its wood wholly replaced by that substance. The surface is marked with those large circular discs which are characteristic of all the pine tribe, and those of this fossil are arranged as in the living genus, Araucaria. I know no species of that genus, however, in which the fibres composing the wood are nearly so large as here. There is also a great peculiarity in the cellular tissues forming the medullary rays: the cells of which are so much transversely elongated as to be six or seven times as long as broad; and their surfaces present impressions of the discs of the woody fibres between which they are interposed.
"It is not easy to conceive how the silicification of this part of the tree was effected; for the infiltration of a fluid charged with silica between the fibres would have consolidated them all into one mass. Again, if the fluid were confined to the cavities of the fibres, forming only casts of these, spaces answering to the thickness of the walls would be left between every one. A transverse section of the agatized portion shows the walls of the fibres to be of considerable thickness, and to be composed of a transparent silica, which also occupies the interstices; whilst their cavities are full of an opaque mass of the same substance."
The morning we had appointed for our visit to the