A | subdivisions in descending | | | | thick series of slates and phyllites | order: (1) Keweenwan, lying | | | | lies below the oldest Palaeozoic rocks | unconformably on (2) Animikie, | | | | in central Europe, with coarse | separated by a strong | | | | gneisses below. | unconformability from (3) Upper| | | | | Huronian, (4) Lower Huronian | | | | | with an unconformable base, (5)| | | | | Goutchiching, (6) Laurentian. | | | | | In the eastern part of Canada, | | | | | Newfoundland, &c., and also in | | | | | Montana, sedimentary formations| | | | | of great thickness below the | | | | | lowest Cambrian zone have been | | | | | found to contain some obscure | | | | | organisms. | +---+---+-------------------------------------------+----------------------------------+ From these general considerations we proceed to inquire how the existing topographical features of the land arose. Obviously the co-operation of the two great geological agencies of hypogene and epigene energy, which have been at work from the beginning of our globe's decipherable history, must have been the cause to which these features are to be assigned; and the task of the geologist is to ascertain, if possible, the part that has been taken by each. There is a natural tendency to see in a stupendous piece of scenery, such as a deep ravine, a range of hills, a line of precipice or a chain of mountains, evidence only of subterranean convulsion; and before the subject was taken up as a matter of strict scientific induction, an appeal to former cataclysms was considered a sufficient solution of the problems presented by such features of landscape. The rise of the modern Huttonian school, however, led to a more careful examination of these problems. The important share taken by erosion in the determination of the present features of landscape was then recognized, while a fuller appreciation of the relative parts played by the hypogene and epigene causes has gradually been reached.