276 HOBBS— THE EVOLUTION AND THE [April 24. 



" Beagle " made observations-^ which advanced the knowledge of 

 volcanic distribution, as we shall see, very nearly to that of the 

 present day. 



As early as 1825, that pioneer and master of vulcanology, Paulett 

 Scrope, discussed the arrangement of volcanoes in the following 

 manner •}- 



The generality of volcanos have a decided linear arrangement; one vent 

 following the other in the continuation of the same straight or nearly straight 

 line; and when volcanos have been formed on neighbouring points out of 

 this principal line, they are in almost all cases situated upon other rectilinear 

 bands parallel to the first. 



Later Scrope expressed his doubt of the existence of v. Buch's 

 class of central volcanoes, for which it had been claimed no align- 

 ment could be discovered.-^ In 1844 Darwin proved the existence 

 of neighboring parallel fissues outlined by volcanoes, and was further 

 able to show by his studies of the Galapagos Islands that the arrange- 

 ment of the vents there brought out the existence of a network of 

 fissures composed of two rectangular series with the principal vents 

 at the intersecting points.^* The directions of the two series were 

 northwest by north and northeast by east. Virlet d'Aoust had 

 already discovered the same kind of structure in the arrangement 

 of the volcanoes within the Grecian archipelago.-^ 



Inasmuch as a mesh-like disposition of volcanic vents within a 

 network is of the first importance in its relation to the mass dis- 

 placements which occasion earthquakes, it is pertinent to examine 

 the more recent literature of the subject with a view to establishing 

 its truth or falsity. The newer and more accurate methods for pre- 

 paring maps which have been introduced since the time of Darwin, 

 make such a review at the present time in every way desirable. 

 There are two regions especially which have been recently carefully 

 studied by authorities of the first rank in the field of vulcanology. 

 I refer to Iceland, surveyed at his personal expense throughout a 



"' " Geological Observations on the Volcanic Islands, etc.," 1844, pp. 



140-145- 



^" " Considerations on Volcanos," London, 1825, p. 126. 



" " Volcanos," London, 1862, p. 258. 



"*L. c, edition of 1900, p. 131. 



'^ Bull. Soc. Geol. France, Vol. 3, 1832-33, pp. 103-110, 201-204. 



