Fig. 373.
Fossil tree at right angles to planes of stratification. Coal measures, Nova Scotia.
In regard to the plants, they belonged to the same genera, and most of them to the same species, as those met with in the distant coal-fields of Europe. In the sandstone, which filled their interiors, I frequently observed fern leaves, and sometimes fragments of Stigmaria, which had evidently entered together with sediment after the trunk had decayed and become hollow, and while it was still standing under water. Thus the tree, a b, [fig. 373.], the same which is represented at a, [fig. 374.], or in the bed e in the larger section, [fig. 372.], is a hollow trunk 5 feet 8 inches in length, traversing various strata, and cut off at the top by a layer of clay 2 feet thick on which rests a seam of coal (b, [fig. 374.]) 1 foot thick. On this coal again stood two large trees (c and d), while at a greater height the trees f and g rest upon a thin seam of coal (e), and above them is an underclay, supporting the 4-foot coal.
Fig. 374.
Erect fossil trees. Coal-measures, Nova Scotia.
If we now return to the tree first mentioned ([fig. 373.]), we find the diameter (a b) 14 inches at the top and 16 inches at the bottom, the length of the trunk 5 feet 8 inches. The strata in the interior consisted of a series entirely different from those on the outside. The lowest of the three outer beds which it traversed consisted of purplish and blue shale (c, [fig. 373.]), 2 feet thick, above which was sandstone (d) 1 foot thick, and, above this, clay (e) 2 feet 8 inches. But, in the interior, were nine distinct layers of different composition: at the bottom, first, shale 4 inches, then sandstone 1 foot, then shale 4 inches, then sandstone 4 inches, then shale 11 inches, then clay (f) with nodules of ironstone 2 inches, then pure clay 2 feet, then sandstone 3 inches, and, lastly, clay 4 inches. Owing to the outward slope of the face of the cliff, the section ([fig. 373.]) was not exactly perpendicular to the axis of the tree; and hence, probably, the apparent sudden termination at the base without a stump and roots.
In this example the layers of matter in the inside of the tree are more numerous than those without; but it is more common in the coal-measures of all countries to find a cylinder of pure sandstone,—the cast of the interior of a tree, intersecting a great many alternating beds of shale and sandstone, which originally enveloped the trunk as it stood erect in the water. Such a want of correspondence in the materials outside and inside, is just what we might expect if we reflect on the difference of time at which the deposition of sediment will take place in the two cases; the imbedding of the tree having gone on for many years before its decay had made much progress.