398 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



This view of mountain formation is essentially identical with 

 that here adopted, except that I conceive the' interior part of a 

 mountain, whether a peak or a chain, to be filled underneath with 

 porous lava, which explains the feebleness of the attraction of 

 mountains and the readiness with which they are converted into 

 volcanoes when once their tops are burst open during the paroxysms 

 of an earthquake. The present views therefore confirm and some- 

 what extend those Held by the elder Darwin seventy years ago. In 

 Chapter VI of his " Geological Observations on Volcanic Islands " 

 the great naturalist says : 



" 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 con- 

 nection between the volcanic forces acting under this island and under the 

 continent, as was shown during the earthquake of 1835. The islands, more- 

 over, of some of the small volcanic groups which thus border continents, 

 are placed in lines, related 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 Verde Archipelagoes, and the best marked line of the 

 Canary Islands. If these facts are 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 neighboring continents 

 — a relation which Von Buch considers characteristic of his great volcanic 

 chains. 



" We ought not, however, to suppose, in hardly any instance, that the 

 whole body of matter, forming a volcanic island, has been erupted at the 

 level on which it now stands ; the number of dikes, which seem invariably to 

 intersect the interior parts of every volcano, show, on the principles of M. 

 Elie de Beaumont, that the whole mass has been uplifted and fissured. A 

 connection, moreover, between volcanic eruptions and contemporaneous ele- 

 vations in mass^ has, I think, been shown to exist in my work on Coral 

 Reefs, both from the frequent presence of upraised oreanic remains and 

 from the structure of the accompanying coral reefs. Finally, I may remark, 

 that in the same Archipelago (Galagapos), eruptions have taken place within 

 the historical period on more than one of the parallel lines of fissure: thus, 

 at the Galapagos Archipelago eruptions have taken place from a vent on 

 Narborough Island, and from one on Albemarle Island, which vents do not 

 fall on the same line; at the Canary Islands, eruptions have taken place in 

 Teneriffe and Lanzarote; and at the Azores, on the three parallel lines of 

 Pico, St. Jorge, and lerciera. Believing that a mountain axis differs essen- 



^ A similar conclusion is forced on us by the phenomena which accom- 

 panied the earthquake of 1835, at Conception, and which are detailed in my 

 paper (Vol. V, p. 601) in the Geological Transactions. 



