8b GEOLOGY. 



hypothesis in this form is to be retained, has, at the same time, grown 

 more imperative with progressive investigation; for it is obvious that 

 all the vast series of sediments must have been derived from the original 

 crust and from such extrusions as have since come from beneath it, and 

 it is becoming more and more evident that the original source of the 

 main portion of this material was the present land area and its immedi- 

 ate borders. There is now no satisfactory evidence of any general 

 reversal of continental and oceanic areas, as was once rather freely 

 postulated. Abysmal deposits do not appear in the continental series, 

 if one or two equivocal cases be set aside; and if abysmal areas have 

 not been added to the continents, continental areas cannot have been 

 sunk to abysmal depths, without destroying the critical relations of the 

 sea to the land which seem to have been constantly maintained. There 

 is now, therefore, little or no plausible ground for supposing that large 

 abysmal portions of the crust were thrust up into high land and sup- 

 ported there till great sedimentary series were derived from them, 

 and then withdrawn to abysmal depths again. This argument should 

 not be pushed so far as to shut out mutual encroachments and reces- 

 sions of shallow sea on land — which have been numerous — nor minor 

 changes in the relations of the deep basins and the continental plat- 

 forms; but it is probably quite safe to conclude that the sediments 

 now buried beneath the sea, and not reckoned in the known series, 

 are greater in amount than any sediments that may have been derived 

 from portions of the primitive land areas now buried beneath the sea; 

 in other words, it is probably quite safe to assume that at least as much 

 derivative material as is now represented by the known sediments, 

 has come from the present land areas. There should, therefore, be 

 large areas of the original crust now occupying the surface, and still 

 other areas lying beneath the sedimentary series in such a way as to be 

 accessible incidentally here and there. If the trend of further investi- 

 gation shall follow the present tendency, and exclude the accessible 

 rocks of the Archean areas from the original crust, the molten theory, 

 in its original form, will have lost its observational support. 



2. Atmospheric Difficulties. 



The second point of growing dissatisfaction is a corollary of the 

 preceding one, for both spring from the assumption that the atmos- 

 pheric and hydrospheric gases were excluded from the molten globe. It 



