James Hutton (1726-1797) had set forth (1788) the principle that during all geological time there has been no essential change in the character of events, and that uniformity of law is perfectly consistent with mutability in the results.
The Spermatophyta fall into two classes, Gymncsperms (q.v.) and Angiosperms; the former are the more primitive group, appearing earlier in geological time and showing more resemblance in the course of their life-history to the Pteridophyta.
The existence of man in remote geological time cannot now be questioned, but, despite much effort made in likely localities, no bones, with the exception of those of the much-discussed Pithecanthropus, have been found which can be regarded as definitely bridging the gulf between man and the lower creation.
Trend to crustal deformations which in very early geological time gave a beginning to what later came to be the Appalachian mountain system; but this system had Its climax of deformation so long ago (probably in Permian time) that it has since then been very generally reduced to moderate or low relief, and owes its present altitude either to renewed elevations along the earlier lines or to the survival of the most resistant rocks as residual mountains.