OCEAN DESTROYS AS VOLCANOES BUILD UP 271 



tory, they have been occurring throughout a vast interval of time, and 

 hence in the aggregate have been many. 



If the quantity of material actually contributed from the earth's in- 

 terior and added to this surface, as witnessed by the 1902 eruption of 

 Martinique and Saint Vincent, was enormous, what must its aggregate 

 have been in the past ? 



If " water gas, which, ultimately escaping as steam, has been estimated 

 at Tinrv of the whole cloud that hangs over an active volcano/' as alleged 

 by Geikie* then the solid matter discharged into the air is but ttoit °f 

 the volcanic cloud. It has already been shown, however, from observa- 

 tions of the recent eruptions of mont Pele and Saint Vincent, that the 

 larger proportion of the solid matter escaping as dust from the craters 

 was distributed by the atmosphere for hundreds of miles around instead 

 of immediately settling down around the vents. If y% of this yoVff °f 

 solid matter is wafted away from the island piles (and this estimate is 

 small), then it is evident that the volcanic rocks and ashes piled up 

 around the vents and constituting the present islands, without any con- 

 sideration of the wear and tear of surface erosion, can represent only 

 10000 of the actual matter which came up through these vents from the 

 earth's interior. Hence these relatively large islands represent only an 

 infinite fraction of the total solid matter discharged by these old vents 

 during long eons of time. But even this little fraction must be again 

 subdivided, for destructive forces long in operation have been tearing 

 away almost as fast as the volcanoes could build them up. 



The trade winds, blowing with full severity against the eastern shore, 

 create an enormous surf, which is constantly and continuously eating 

 away the shore line and cutting down below sealevel the volcano-built 

 islands. This destructive work and its combative attacks on the grow- 

 ing areas of land is a most instructive feature of the region. In fact, 

 this destructive process is secondary only to that of the constructive 

 process of volcanic pile-up, and the present aspects of the islands are 

 chiefly a result of the endless battle between these agencies. 



The power of the sea to plane off in horizontal directions obstacles 

 projecting above it is everywhere seen. Huge cubes of rock which have 

 fallen into the sea near Bathsheba, on the Windward coast of Barbados, 

 have been completely cut in two. The processes of the sea in cutting 

 through these rocks by attacking them at surf line is but an illustra- 

 tion of how larger islands have been completely reduced to submarine 

 banks. 



A superb example of sea destruction is the bight known as Porte 



* Text-book, edition 1903, p. 266. 



