I40 T. C. CHAMBERLIN 



These considerations give point to the following observations: 



1. The cases in which true abysmal deposits, or close imitations 

 of true abysmal deposits, now appear above the sea-level do not, 

 when all are put together, appear to attain in area so much as one 

 per cent of the total earth surface. So that, even if we assume that 

 all cases plausibly interpreted as abysmal are truly so, the frac- 

 tion of the crust in which a reversal of the dominant habit obtains 

 is still so small that it cannot be regarded as other than exceptional. 



2. So far as my present information goes, all the cases that call 

 for serious consideration as real or plausible instances of the lifting 

 of abysmal deposits above sea-level lie in the notable hinge areas 

 where exceptional instability now prevails and apparently has 

 prevailed far back in geologic history. By far the best of all cases 

 of supposed oscillation between abysmal and subaerial attitudes 

 is that offered by the "oceanic deposits" of the island of Barbados 

 in the Windward group of the Lesser Antilles. To be associated 

 with this in interpretation are the "oceanic deposits" of Trinidad, 

 Jamaica, Cuba, and Haiti, all in the same hinge area between North 

 and South America and between the Atlantic and Pacific basin 

 segments. These additional oceanic deposits have not been as 

 well studied as those of Barbados, but from what is known they 

 seem to hamper rather than strengthen the interpretation that the 

 Barbados deposits are really abysmal. But to this we will return 

 later. 



The supposed deep-sea deposits of Sicily are perhaps entitled 

 to rank next to those of Barbados in type and importance. These, 

 like the preceding, are associated with similar deposits adjacent 

 to the Mediterranean on the north and on the south. These, like 

 the collateral deposits of the Antilles, perhaps hamper rather than 

 strengthen a strictly abysmal interpretation of the deposits. But 

 neglecting this, the notable feature of the case is that these deposits 

 lie in one of the most remarkably unstable regions of the globe, 

 the hinge area between the more stable parts of Eurasia and the 

 stable part of Africa. This hinge line has its eastward projection 

 along the ancient Tethys Straits and thus becomes connected with 

 the East Indian tract which also is one of notable instabihty. The 



