528 T. C. CHAMBERLIN 
It is a natural result that the continents are pre-eminently the great 
terraces of the globe. The picture of the continents as essentially 
terraces wrought upon diastrophic embossments is no doubt the 
truest that can be formed, and the contest between the diastrophic 
forces that emboss by protrusion and the gradational forces that 
terrace by planation and shelf-building, the chief physical battle of 
geologic history. 
Diastrophic limitations—Let us now consider the degree of 
competency and of incompetency of diastrophism to produce 
shallow seas whose deposits and faunas may be comparable in any 
serious sense with those of the shelf-seas. 
If the earth-body were a perfect spheroid of revolution com- 
pletely adapted to its own conditions, and if the volume of the 
hydrosphere were essentially what it is today, there would be a per- 
fect parallelism between the sea-surface and the sea-bottom of the 
universal ocean that would be the inevitable consequence of these 
conditions, but there would be no sediments of the common kinds 
nor any life of the more familiar fossil types, but only the pelagic 
and the abysmal. The picture of such a state of the earth and of 
such an evolution as might arise from it, if indefinitely prolonged, is 
as far as possible from that which geologic history really presents at 
any known age. The actual earth has a deformed surface of such 
proportions that about one-third is continental protuberance and 
two-thirds abysmal depression, with connecting slopes between. At 
present about one-sixth of the continental protuberance is covered 
by epicontinental seas, and this sixth adjusts the one-third-two- 
thirds ratio to the more familiar one-fourth-three-fourths ratio of 
land to water so successfully inculcated by the geographies. It 
is the one-third-two-thirds ratio of body-protuberance to body- 
depression that concerns us in deformative studies. In these 
studies the modification imposed by the sea-shelf work is an 
incident. 
These proportions have been taken of course from the present 
status. If it is suggested that a quite different ratio may have pre- 
vailed in early geologic times and that the ratio in the Paleozoic era 
may have been so far different as to leave little value in this present 
ratio, it is a ready reply that no special weight is placed on this ratio 
