Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 2.djvu/21

] circumference; but those placed half way between these extremes, on being removed, fell into a snowy-white powdery mass, called "native pounce" by the colonists, resembles amianthus, but is much more brittle. This disintegration of a particular portion of the trunk was not owing to the action of the weather; but to a want of cohesion between the fibres of which the wood is composed.

"Those concentric rings which immediately surround the disintegrated ones, may, with a little force, be divided into laminæ, composed of parallel rows of fibres, beautifully adapted for examination under the microscope: every such ring being divisible, in the direction of the radius, into plates, each consisting of a single row of fibres, held together by the medullary rays, which cross them at right angles like cross-bars. The individual fibres forming one lamina, are of equal length, and in such close juxta-position, that no interstices appear; yet they are separable with the slightest force; proving that the woody substance of the fibre itself is replaced by silica, and that it is not a mere cast of its hollow axis which is preserved.

"In examining silicified woods of the ordinary structure, or such as resemble either the central portion or circumference of this fossil, it is necessary to have thin slices prepared at considerable expense by a skilful lapidary; the object being to obtain such a slice as will display all the characters of the individual fibres. But here such