144 The Distribution of paet i. 



would naturally result that the inferior primary rocks 

 would often be uplifted and brought into view. 



Some authors have remarked that volcanic islands 

 occur scattered, though at very unequal distances, along 

 the shores of the great continents, as if in some measure 

 connected with them. In the case of Juan Fernandez, 

 situated 330 miles from the coast of Chile, there was 

 undoubtedly a connection between the volcanic forces 

 acting under this island and under the continent, as 

 was shown during the earthquake of 1835. The 

 islands, moreover, of some of the small volcanic groups 

 which thus border continents, are placed in lines, re- 

 lated to those along which the adjoining shores of 

 the continents trend ; I may instance the lines of 

 intersection at the Galapagos, and at the Cape de 

 Yerde Archipelagos, and the best marked line of the 

 Canary Islands. If these facts be not merely accidental, 

 we see that many scattered volcanic islands and small 

 groups are related not only by proximity, but in the 

 direction of the fissures of eruption to the neighbouring 

 continents — a relation, which Von Buch considers, cha- 

 racteristic of his great volcanic chains. 



In volcanic archipelagos, the orifices are seldom in 

 activity on more than one island at a time ; and the 

 greater eruptions usually recur only after long intervals. 

 Observing the number of craters, that are usually found 

 on each island of a group, and the vast amount of 

 matter which has been erupted from them, one is led 

 to attribute a high antiquity even to those groups, which 

 appear, like the Galapagos, to be of comparatively recent 

 origin. This conclusion accords with the prodigious 

 amount of degradation, by the slow action of the sea, 

 which their originally sloping coasts must have suffered, 

 when they are worn back, as is so often the case, into 

 grand precipices. We ought not, however to suppose, 



