130 AKT. 3. — B. KOTÔ : 



113.7 A-??2., Gilbert attributes the cause of gravity anomaly to varia- 

 tions in the vertical distribution of density. A local, but not re- 

 gional, anomaly of defect, with which we are now concerned, 

 means a defect above and excess below, tlie sum of both being 

 the same everywhere at 122 hn. The inequality adjusts itself 

 by undertow or underflow in the zone of relative mobility which 

 can originate in liquefaction near the surface as a consequence of 

 reduction of density through faulting, and the mobility of the in- 

 tercrustal layer further causes vulcanism.^^ 



A regional anomaly defect of mass is, however, supposed 

 to be adjusted by undertow above, below or within the zone of 

 compensation. According to Barrel"^ the undertow is only possible 

 below the zone in the asthenosphere or the zone of weakness. 



Having traced the relations among undertow, mobile zone, 

 diastrophism and finally vulcanism, we now turn to our subject 

 proper. 



^"equL""^ In the annexed Sketch-map, PI. XIII., the ' curves 



Subsidence ^£ equal subsidcuce ' worc drawu approximately through 

 the points of equal settling of terrene.^^ To each point are 

 attached the figures in millimetres reduced to the level of Tokyo, 

 which express the differences between the levelings done during 

 1892 to 1900 and the resurvey during July and August of 1914. 



The writer has drawn ten curves, viz., of 800, 700, 600, 500, 

 400, 300, 200, 150, 100, and mm. The curves describe roughly 

 concentric circles which are at first closely packed together near 

 Cape Osaki at the north of Kagoshima, and there lies a maxnnum 



1) Volcanoes usually make their appearance in the region of mass defect rather than in 

 the compacted area. 



2) Jour. Geol. Chicago, 1914. 



3) A similar attempt has already been made by F. Omori in his recent papers. See Bull. 

 Imp. Eiirthq. Com., Vol. \H1. No. 1, p. 29, and • The Tôyû-gakugei-Zasshi ' {The Oriental Science), 

 :No. 402, March, 1915. 



