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J. W. SPENCER^ M.A., ON THE GEOLOGICAL 



restricted areas than the old pre-Tertiary igneous eruptions, as 

 we find late volcanic accumulations in the first place restricted 

 to the inner chain of islands, and even there not covering their 

 whole surface, without even building up connections between 

 what are now the adjacent islands. From observations 

 especially in St. Kitts, Guadeloupe and Dominica, and the 

 resemblance of the igneous formations in the other islands to 

 those first mentioned, it is apparent that the volcanic ridges 

 and cones built upon the surfaces of the old igneous formations, 

 owe their size and great height, reaching to 4,000 or 5,000 feet, 

 to the volcanic eruptions accompanying the great changes of 

 level of land and sea which have occurred since the beginning 

 of the Pleistocene or Glacial period. The building up of the 

 ridges of these inner islands has been due entirely to volcanic 

 forces which have scarcely affected the portions of the island 

 beyond the ridges themselves ; but within this limit we find that 

 the stratified beds, some of which are mechanical formations 

 derived from the ancient rocks and stratified beneath the sea, 

 had been everywhere tilted outward from the centre of the 

 volcanic cones which rest upon their surfaces. These sloping 

 volcanic beds have not been confounded with the tufaceous 

 deposits which have been accumulated upon the slopes of the 

 cones of which they make up almost the entire mass, as lava 

 is found at only occasional points. While the volcanic 

 activity at the present time is startling from the disasters 

 that the eruptions have produced, yet it is insignificant compared 

 with the whole amount of material which has been erupted to 

 build up the cones. 



Interesting examples of the localized effects of the eruptions 

 in lifting and disturbing the strata, may be seen in 

 St. Eustatius and in St. Kitts. In the latter island there is a. 

 prominence rising to a height of 700 feet with a diameter of 

 much less than half a mile, called Brimstone Hill, which is 

 veneered to a height of 450 feet by a bed of limestone, having 

 a thickness of about 30 feet, dipping outward in all directions 

 at high angles, which was the former sea bottom. This 

 prominence was elevated by the volcanic forces pushing up a 

 cone, which, however, was not surmounted by a crater. This 

 elevation took place as far back as the mid-Pi eistocene epoch ; 

 and as it occurs on the flank of the main volcanic ridge of 

 St. Kitts, it suggests that the volcanic activity had greatly 

 diminished in that island long before the present day, although 

 more recent eruptions had built up the summit of the cone 

 where we now find the crater. Twelve miles distant across the 



