2G2 Dr James Macanlay on the Physical Geography^ 



the ocean) that, after the time of their deposition, the relative 

 level of sea and land was in many parts by violent means 

 altered, and the island partially exposed to the influence of 

 those causes, by the operation of which, many volcanic tracts 

 that have been raised above the sea have been again made 

 wholly to disappear. This violent agency on the surface of 

 the land is further manifest from the vast size of the valleys 

 and ravines, which the small streams that now run in them 

 could never in any course of time have been able to excavate ; 

 as well as from the abrupt and rugged character of the gigan- 

 tic cliffs which now form in most parts the outline of the 

 island. These could only be the effects of earthquakes or 

 other great convulsive agencies. Since the commencement of 

 the present geological epoch, the island has been in repose, 

 there being no indication of recent eruptions, and none of the 

 products observed in modern volcanic districts. 



The changes at present operating on the surface of the land 

 arc only those of a gradual nature. For many years no shock 

 of an earthquake or other violent disturbing cause has been 

 experienced. When these have occurred, they have been con- 

 nected with distant volcanic action. In many places, the wa- 

 ters of the ocean are rapidly wearing the sea-cliffs. In the 

 interior, the rivers work a considerable change at times upon 

 tlie surface. From the steepness of the sides of the ravines, 

 there are frequent slips of the soil, the havoc of which adds to 

 the romantic wildness of the scenery of these places. A Ithough 

 none of the rivers are ordinarily of great size or power, they 

 are sometimes swollen so much as to bear down immense quan- 

 tities of soil and rock, and work great damage in their course. 

 In the year 1803, for instance, all the streams were swollen by 

 a great flood, by which an immense amount of damage to pro- 

 perty was sustained, and in some places bridges were destroyed 

 and many houses borne down by the force of the waters. 



The sea around the island is almost every where immediately 

 deep, as might be expected from the abrupt declivity of the 

 shores. The configuration of the adjacent submarine tract, so 

 far as known, is extremely irregular, there being no plains of 

 great extent, and those which do exist being composed of rough 



