SUBMARINE LAVA. 325 



a great extent of the ocean-bed, according to the 

 o{)inion of Mr. Poulett Scrope, who has expressed him- 

 self to the following effect in his work on "Geology 

 and the Extinct Volcanoes ot* Central France." " We 

 ought to observe," he says, " that lava-streams at the 

 bottom of the sea must have a greater breadth, com- 

 pared with their thickness, than those which are cooled 

 under atmospheric pressure, and that this lateral ex- 

 tension is proportioned to the depth of the water." 



It ought also to be observed that lava-streams 

 which have cooled at great depths under the water 

 present little scoriae. This, in fact, has been observed 

 in the old volcanic rocks of submarine origin. This, 

 however, may be caused by the influence of ocean- 

 currents, or other movements of the water." 



Some knowledge of the peculiar action of submarine 

 volcanoes might be acquired by investigating their 

 products, which may be brought to light by the sub- 

 sequent elevation of the ocean-bed above the level of 

 the sea. Examples of this are frequent in the coral 

 isles of the Pacific. The basaltic columns of the south 

 and north coasts of Ireland, of the Faroe Isles, of the 

 north-east of Teneriffe, and numerous other localities, 

 tend to demonstrate that the phenomena displayed 

 by lava, when it is ejected beneath the sea, are very 

 nearly similar to what occurs on the solid earth. The 

 principal differences seem to be : 



