GEOLOGY 107 



1910, steps have been taken to establish an International Vulcanological Institute at 

 Naples, for the systematic investigation of volcanic phenomena, especially those of 

 Vesuvius. It is believed that the detailed observation of such phenomena, carefully 

 recorded, may eventually lead to the determination of the successive stages in the 

 approach of an eruption, and may thus become of much practical value. The gases 

 exhaled from various volcanoes will be subjected to thorough analysis, and light may 

 probably be thrown in this way on the origin of certain ore-deposits. Prof. Gaetano 

 Platania is also establishing an institute in Sicily for the special study of Etna. 



Earthquakes. A valuable " Catalogue of Destructive Earthquakes," prepared by 

 Prof. John Milne, has been published as an Appendix to the Report of the Seismological 

 Committee of the British Association for 1911. The entr'es, numbering nearly 6,000, 

 extend from November 10, A.D. 7, to December 31, 1899. The list represents extensive 

 research carried on for many years, and is specially notable for its records of earthquakes 

 in China and Japan. Feeble disturbances have been excluded, the items being confined 

 to those of sufficient violence to effect structural damage. The order of intensity is 

 indicated by reference to a definite scale. It is believed that the earthquakes recorded 

 in this Catalogue have generally been connected with the formation or extension of lines 

 of fault and fracture in the crust of the earth, and have consequently much interest to 

 the geologist. 



In the Report of the Seismological Committee of the British Association at Dundee 

 and in the Halley Lecture at Oxford in 1912 (Bedrock, No. 2, p. 137) Prof. J. Milne made 

 an ingenious suggestion as to a possible cause of earthquake activity. It is found that 

 large earthquakes, or megaseisms, resulting from a sudden relief of strain in the earth's 

 crust, are most frequent in regions where the geothermic gradients are steepest, suggest- 

 ing that the disturbances are connected with the outward flow of the earth's internal 

 heat. Observation on the solidification of blast-furnace slag showed that the material 

 suddenly contracted intermittently, and that the cooling mass cracked superficially, 

 with extrusion of heated viscous matter, due to grip of the shrinking outer shell on the 

 interior. 



Such phenomena seem to admit of application to the rocks of the earth's crust. If 

 the superficial shell contracts spasmodically at regular intervals in passing from the 

 liquid to the solid state, or on cooling after solidification, it may suddenly fracture itself 

 by a tight grip on the unyielding nucleus. Such action possibly throws light on 

 many seismic phenomena, and may also explain the extrusion of lava in fissure-eruptions 

 and dykes. Prof. Milne points out that volcanoes are too feeble to produce megaseisms, 

 but that megaseisms often stir dormant volcanoes into activity. 



The earthquakes of the Philippine Islands have been specially studied by the Rev. 

 , M. Saderra Maso, of the United States Weather Bureau. He shows that those of 

 southern Luzon are connected with three great fractures, of which the most important 

 runs through Taal volcano. This volcano was the seat of a disastrous eruption on 

 January 30, 1911. 



The first part of a seismic history of the southern Andes, by the Count de Montessus 

 de Ballore, was published at Santiago de Chile in 1911. 



The Zone of Rock Flo-wage. It has been generally recognised of late years that the 

 solid crust of the earth admits of division into an upper Zone of Fracture and a lower 

 Zone of Flowage. Below a certain depth the pressure becomes so great that the exist- 

 ence of open spaces seems impossible, since the movement of the solid rock by flowage 

 must tend to close all cavities. At what depth the fractures cease is a question of ex- 

 treme interest, and various estimates have been made from time to time, with more or 

 less probability, by such geologists as Heim and Van Hise. The question has recently 

 been studied experimentally, with much ingenuity, by Prof. Frank D. Adams, of 

 Montreal, whose results are published in a paper entitled " An Experimental Contribu- 

 tion to the Question of the Depth of Flow in the Earth's Crust " (Journal of Geology, 

 Chicago, Vol. xx, 1912, p. 97). 



Two rocks were subjected to experiment, viz. an American red granite, representing 



