MICHIGAN ACADEMY OF SCIENCE. 103 



crests to have moved inland in some places to great distances And still 

 a certain degree of uniformity might be maintained over long stretches. 



Suppose now, succeeding upon such a stage of high relief, a rise of sea 

 level until the basins are slightly over-full. No matter where upon the 

 coastal slope the new strand formed it would be roughly parallel to the origi- 

 nal torn outline because its plane would intersect a slope derived from that. 

 The brink or crest contour having moved inland, all slopes having been merged 

 into one another, that crest might be drowned to a depth of a hundred fath- 

 oms or to some other depth. On the seaward side of this the slope would 

 be more or less rapid, on the land side gentle. The curves of the new coast 

 line would tend to remain roughly parallel to the original brink. 



Then comes sedimentation. The submerged slopes receive the materials 

 washed down from the land. Sediments from large areas are deposited on 

 small, making up in thickness what they lose in area. The inevitable result 

 must be the alteration of the submerged contours out of proportion to the 

 changes produced on the lands by the removal of the transported materials. 

 Ultimately we must expect the hundred fathom curve to be so changed that 

 it cannot at all be taken as representing, what it once did, an approxima- 

 tion to the original torn outline. But the coast line might continue longer 

 to retain its ancient parallelisms. 



In matching together tAvo such coasts we should be struck at once with 

 the concentricity of the greater curves, for these curves would be derived 

 from the former crests moved inland. And is this not exactly what we find 

 upon the globe today? And would not the distances, center to center of 

 given land masses, be quite as rigidly prescribed as if we were dealing with 

 freshly torn edges? It seems that such would be the case. 



To sum up then, in reply to the challenge of the use of the coastlines, we 

 may emphasize the following points: 



1. The preference for the hundred fathom or other submarine curve is 

 based upon a priori grounds as opposed to the analytical study of observed 

 facts. It puts a premium on prejudice. 



2. Speaking generally, the proper use of the coast lines necessarily pro- 

 vides for the submerged margin. 



3. The submerged contours are highly changeable and unreliable because 

 of sedimentary alteration. 



4. The submerged contours are fully as objectionable on the score of 

 vertical crustal movements as are the coast lines. 



5. Change of coast lines by encroachment of waves and tides varies in 

 detail but seems to be fairly uniform over greater marginal features. 



6. A hypothetical rise of sea level in the less remote geological past (close 

 of the Pleistocene) would be compatible with the observed facts. 



