206 The Philippine Journal of Science ms 



and must be taken into account when drawing the tectonic lines 

 of the Philippines. 



As a general study of the geology and vulcanism of the Phil- 

 ippines, Becker's report 13 is the most complete work that has 

 appeared. In it is to be found an excellent resume and criticism 

 of all the writings on the subject that had been published up to 

 that date. A shorter but more recent work is the article by 

 Smith. 14 



The names of several Austrian, German, and French geologists 

 and explorers to whom we owe the first geological data on the 

 Philippines should also be mentioned. The principal ones are: 

 von Richthofen, Carl Semper, Oebbecke, K. Martin, Jagor, Roth, 

 R. von Drasche, and J. Montano. Likewise, attention is called 

 to the works of the eminent French seismologist, Montessus de 

 Ballore, who published many articles on Philippine earthquakes 

 during the years 1895 to 1901. In one of his books 15 he gives 

 a summary of these articles on the earthquakes of the Philip- 

 pines. This author must be considered as the first to apply to 

 this Archipelago the principles of modern seismology by refer- 

 ring its earthquakes, not so much to imaginary volcanic agencies, 

 as previous authors had done, but to the principal and geological 

 accidents ; in other words, to tectonic lines. Hence, the chapter 

 referred to above must in justice be reckoned the first and most 

 important contribution to the study of Philippine seismology. 



SUMMARY OF THE PHYSIOGRAPHY OF THE PHILIPPINE ISLANDS 



To present a clear idea of the underlying causes of seismic 

 disturbances in the Philippine Islands, it is necessary to make 

 some general statements. The Philippine Islands form a link 

 in the chain of outliers of the old Australasian continent. 

 According to the "horst" theory of the formation of continents 

 and ocean basins, the Philippine Islands lie at the very edge 

 of the Asiatic horst. In June, 1912, the German survey ship 

 Planet sounded to a depth of 9,780 meters about 60 kilometers 

 off the northeast coast of Mindanao. 16 Soundings to the west- 



" Report on the geology of the Philippine Islands, 21st Annual Rep. U. S. 

 Geol. Surv. Washington (1901). 



" The essential features of the geology of the Philippine Islands, This 

 Journal, Sec. A (1910), 5, 307. 



18 Les tremblements de terre. Paris (1906). 



"Zeitschr. Ges. Erdk. Berlin (1912), No. 6, 471; No. 8, 629-631; carte 

 des Bondages du "Planet" a 1'Est des Philippines, a 1 : 15,000,000, Abt. 31. 



