the Igneous Platform. 199 



place in one part of it may be very different from those in 

 another part. As the researches of Dittmars and others have 

 shown, the gases of the air are dissolved in sea-water and it 

 contains oxygen in considerable quantity, even to considerable 

 depths. At first thought this might appear to give sea- water 

 a capacity for oxidation, but in considering the matter the 

 effect of organic life must be taken into account. Thus 

 Buchanan* has shown that in the seas about Scotland in the 

 bottom deposits sulphur and sulphides are being formed, and 

 this process reduces the oxidized products of land waste to 

 blue muds. Various other instances might be cited to show 

 that at the bottom in shallower waters, where life abounds, 

 reduction, not oxidation, is taking place. In some waters, as in 

 those of the Black Sea, a considerable amount of hydrogen 

 sulphide is found in solution, which has been ascribed to the 

 action of bacterial life. It seems, therefore, most probable, if 

 not certain, that in shallow waters along coasts at the bottom 

 there would be not only no oxidation of buried lavas and 

 sediments, but a tendency to a reducing action. That deposited 

 sediments are not always reduced shows merely that the deposit 

 is too rapid and the action too feeble to convert them. 



If it be admitted, as suggested above, that the oxidized 

 material represents the product of land waste, then the conclu- 

 sion follows that Bermuda w T as once an island, composed of 

 volcanic rocks rising above the level of the sea, which has 

 been entirely cut away by the erosive action of the waves. 

 Under this conception everything disclosed by the boring falls 

 logically into place. At the bottom and up to TOO feet lie the 

 original lava flows which built up the cone, unoxidized because 

 the rocks have been protected by the sea from the work of the 

 atmosphere. Above them comes a relatively thin band of 

 deposit, perhaps 75 feet thick, consisting of water-worn, but 

 also unoxidized or but little oxidized debris of volcanic rock, 

 sands, and gravels. This is what we should naturally expect, 

 for this represents the first attack of the waves upon the 

 upward growing volcano, or the early material eroded by them 

 from the new land. Some of the particles of the deposit may 

 practically have never been exposed to the action of the atmos- 

 phere, while others were affected by it only a short period of 

 time before being carried out from the beach and deposited 

 under water. 



As time advances, however, there must come a change. 

 The lighter, more porous, less firm upper portion of the lava 

 flows, indicated by the amygdaloidal structures, and which 



* British Assoc, 1881, p. 584. 



