278 I^r. William B. Carpenter [Jan. 23, 



sea-level, such subsidence would be balanced (according to the current 

 idea of compensatory alternation) by an elevation up to that level of a 

 portion of the average Ocean-floor, amounting to no more than l-36th 

 of its existing area. On the other hand, the sinking of such an area 

 as that of Papuo- Australia (which forms about 1-1 7th of the existing 

 land-surface) to the depth of the average Ocean-floor, would require 

 to balance it an elevation of the whole remainder (13-14ths) of the 

 existing Land to double its present average height above the sea- 

 level. 



B. Wherever the uniform elevation of an extensive Land-area in- 

 dicates its upheaval by a force acting vertically throughout, the amount 

 of such elevation seems to have been very limited,' — no such level area 

 showing itself at any considerable height above the sea. Conversely, 

 there is no adequate reason to believe that any extensive area has ever 

 uniformly subsided beneath the sea-level, to any greater depth than 

 that at which lie the submerged portions of some existing Continental 

 platforms. 



C. On the other hand, all great elevations, whether rising from 

 Continental platforms or from the Oceanic sea -bed, are clearly attribu- 

 table to lateral thrust; and such are everywhere of very limited 

 extent, forming mountain-chains or high table-lands in Continents, 

 and volcanic islands in the Oceanic area, — in neither case having the 

 least resemblance to continental plateaux. And, conversely, the very 

 deep depressions in which long series of stratified deposits have 

 accumulated, only occur as consequences of the lateral thrust which 

 produces plication, and which elevates mountain-ranges as part of the 

 same operation. Local subsidences of this kind, therefore, give no 

 support to the idea of such vast general subsidences, as would be 

 required to create a deep Oceanic depression over any area now occu- 

 pied by a Continental platform. — Inland seas, in fact, may be regarded 

 as troughs of this kind, which have been formed in regions of extra- 

 ordinary disturbance, in which the troughs have been formed more 

 rapidly than they can be filled by the accumulation of sediment from 

 the elevations of which they are the complements. The largest of 

 them (the Mediterranean and Central American) may possibly have 

 been original breaks in their Continental platforms. 



Thus, then, all our knowledge of the existing relations between 

 Continental plateaux and Ocean-basins, and of the forces by which 

 those relations might probably be disturbed, points distinctly to the 

 inference that these relations have never been very different from 

 what they are now. And the entire conformity of the results of this 

 reasoning from the present to the past, with those of Professor Dana's 

 reasoning in the contrary direction from the primal assumption 

 (which no man of science would now call in question) of the Earth's 

 original fluidity, affords strong confirmation of its validity. 



I am far from affirming that considerable local changes may not 

 have occurred in past epochs, which may have had very important 



