686 THOMAS CHROWDER CHAMBERLIN 
feet to a quite definite terrace-angle about too fathoms below the 
sea-level; (2) continental platforms whose upper faces slope gently 
up from this angle to the coast-line and thence ascend into the various 
reliefs of the land. _ If we thus agree that the upper face of the conti- 
nental platform is bounded by the edge of the continental shelf, 
and that this edge is equally the boundary of the abysmal basins, 
whether the waters overlap the edge or not, we may also agree that 
the edge of the oceanic waters, whether they agree with the edge of 
the abysmal basins or not, form the chief line of demarkation between 
the great erosions and the great depositions the world over. It is 
not the only line of such demarkation, to be sure, for degradation 
gives place to aggradation at many other local horizons, but in this 
discussion let us agree to deal only with factors of the larger order 
and to neglect incidentals; let us deal with body deformation, rather 
than local or provincial warpings. We all recognize further that the 
sea-level is not only a dividing plane between two great divisions of 
physical agencies, but between two great biological divisions. 
To this list of agreements, there are two other propositions which 
we cannot add quite so unhesitatingly, because we need to weigh them 
well, and if we cannot all agree respecting them, we must agree to 
differ, for they are fundamental to the further discussion. ‘These 
relate to the effects of body deformation on the relations of land and 
sea. 
If deformation were confined to the abysmal bottoms and were 
compensatory, no effect would be felt on the relations of land and 
sea. If deformation were confined wholly to the interior of the 
continents, it would be similarly ineffectual. Deformations so 
limited are, however, likely to be only provincial, and fall outside 
our discussion. 
There remain two conceptions of general or body deformation 
between which choice must be made. In the one, the deformations 
are supposed to be indifferent to their predecessors, and to disregard 
the configurations produced by previous deformations. ‘Their suc- 
cessive effects upon continental outlines and basin capacities are 
thus heterogeneous and the combined results irregular and uncertain. 
It is not clear to me how they can be made a very trustworthy basis 
of systematic correlation. The submergent phase of one continent 
