70 THE BERMUDA ISLANDS. 



and geologists. But it does not carry with it the assutaption 

 of a necessary permanence in the positions of continents and 

 oceans; it does not imply that the oceanic basins were 

 originally of the extent that they are to-day, as we are led to 

 believe by many geologists. It is far more probable that tiie 

 existing dimensions have been brought about through pro- 

 gressive or cumulative subsidence, which has gradually swept 

 away land-masses that at one time occupied some of the pres- 

 ent area of the sea. The long lines of ridges which have been 

 revealed to us by deep-sea soundings, and the placing on these 

 of many of the oceanic islands (volcanic peaks), together with 

 the evidence which the past and present distribution of animal 

 life carries with it, all support this conclusion. It seems, in- 

 deed, impossible to account for the existence of oceanic (vol- 

 canic) islands, or for the negative islands which rise as promi- 

 nences from the oceanic floor to within a comparatively short 

 distance of the surface, except on the assumption of subsidence. 

 What is the significance of buttresses like St. Helena, Ascen- 

 sion, the Caroline Islands, or the giant peaks of the Sandwich 

 Islands rising from depths of two or three miles, or more? 

 Can it be assumed that they have been steadily built up vol- 

 canically from the ocean fioor, four or five miles in height? 

 This is, perhaps, not impossible, but it hardly appears prob- 

 able. Vulcanism in one form or another doubtless manifests 

 itself over the floor of the ocean, but all indications point to a 

 comparatively limited action in the greater depths. Were 

 submarine eruptioais at all numerous, or of that intensity 

 which might be assumed to be necessary for the construction 

 of a giant mountain-peak, we should be probably made 

 aware of their existence in a manner not less emphatic than 

 in the case of subaerial eruptions. It might be assumed that 

 the long intervals atwliich eruptions take place would prevent 

 special notice of such phenomena, and that, consequently, 

 their effects, even if most momentous, would be placed prac- 

 tically beyond observation. But this is not likely to be the 

 case. When we consider the large number of peaks that in 



