482 ROLLIN D. SALISBURY 



rock has been removed from land to sea, the resulting change of 

 sea-level may be calculated. If the bottom of the sea were not 

 warped so as to increase or decrease the capacity of its basin, the 

 transfer of 66,000,000 cubic miles of rock from land to sea would 

 raise the level of the latter more than 2,400 feet, 1 if no allowance be 

 made for the increased area resulting from the rise. The transfer 

 of 174,000,000 cubic -miles of rock from land to sea would raise its 

 level more than 6,400 feet, while the transfer of 348,000,000 cubic 

 miles would raise its level nearly 13,000 feet, or more than two and 

 one-half miles, if its area remained constant. The increase of area 

 which would be involved would, of course, reduce these figures 

 sensibly. 



If the sea-level were to rise 2,400 feet at the present time, about 

 two-thirds of all the present land would be submerged, and if it were 

 to rise 13,000 feet, only about 2 per cent, of the present land would 

 remain above it. Even if allowance is made for the increase of area 

 which its rise would produce, the transfer of 348,000,000 cubic miles 

 of rock material to the sea would leave no vestige of land in North 

 America east of the Rocky Mountains, and all that remained within 

 the area of the western mountains would be a series of islands where 

 the higher mountains now are. On the basis of even the least of 

 these figures, 2,400 feet, reduced so as to make allowance for the 

 increase of area which would be involved, there would be changes 

 of relative level between sea and land, of an order commensurate 

 with those which are known to have taken place from time to time 

 during the earth's history. 



There is reason to .believe that the continents, at least those whose 

 geological history is best known, have more than once been worn 

 down toward sea-level — worn down so low that rivers became slug- 

 gish, and their mechanical erosion relatively slight. Such a condition 

 would exist if the lands of the present time were worn down to an 

 average height of 500 feet. In this case, about 5,000,000 cubic miles 



1 The materials taken to the sea in solution would not raise the level of the sea 

 so much, cubic mile for cubic mile, as mechanical sediments. Since much the larger 

 part of the sediment taken to the sea has been in the form of mechanical sediments, 

 if we may judge from present conditions, this difference is here neglected; but it seems 

 probable that the amount of dissolved matter h,as been greater than now, relative to 

 the mechanical sediments, if the whole of the earth's history be considered. 



