AXD THE WEST INDIAN ERUPTIONS OP 1902. 



221 



The Cause of Volcanic Action. 



The due consideration of the cause of Volcanic Action would 

 require a treatise and, therefore, all I can do here is to give an 

 outline that may be useful, and to refer my hearers or readers 

 to where I have dealt more fully with the subject.* For the 

 sake of brevity and clearness it may be well to proceed by the 

 method of elimination. 



The liypothesis that must first be disposed of is that of all 

 lava being derived from one great central source, or, in other 

 words, that the globe contains in its interior a vast central body 

 of fused rock-matter that gives to all volcanoes their lava and 

 other ejectamenta. 



This is based on several considerations. The increase of 

 temperature with descent from the surface, found in mines and 

 l)0rincis, will mve a rock-fusino; heat at from 25 to 30 miles 

 depth if continuous. The Xebular Hypothesis of the origin of 

 the Solar System gives an original heat to the earth-mass equal 

 to that of the sum at the time of detachment, and which heat 

 would be greatly above the fusion point of rocks. This high 

 temperature would be very largely retained in the interior of 

 tlie earth-mass, while the exterior would cool and solidify, and 



* Report, British Association, Bath, 1888, p. 670. 



''On the Causes of Volcanic Action," Proc. Geol. Assoc., 1889, vol. xi, 

 p. 1. 



Mount T esuvius, 1889, chapter viii, p. 212. 

 Report, British Association, Oxford, 1894. 



" On the Climate of the Cambrian Period," Knoidedge, November, 



1894, vol. xvii, p. 260. 

 " On the Mean Eadial Variation of tlie Globe, ' Quart. Jour. Geol. 



Soc, 1895, vol. li, p. 99. 

 "On the Cause of EartliQuakes," Knowledge, July 1895, vol. xviii, 



p. 161. 



"Volcanic Phenomena," Jour. City of Lon. Col. Sci. Soc., 1896, vol. iv, 

 p. 1. 



"The Foldings of the Rocks," Knowledge, 1896, vol. xix, p. 162. 

 " On the Source of Lava," and 

 " On the Post Cambrian Shrinkage of the Globe."" 

 "The Mean Radial Variation of the Globe." Eep. Brit. Assoc., 

 Liverpool, 1896. 



Presidential Address, 1896, City of Lon. Coll. Sci. Soc, Jour, of Soc, 

 vol. iv, p. 69. 



" On the Depth of the Source of Lava," Quart. Journ. Geol. Soc, 

 1897. 



" The Crust of the Globe and its Disturbances." 

 Presidential Address, 1897, City of Lon. Coll. Sci. Soc, Jour, of Soc, 

 vol. V, p. 1. 



