IV. PRESIDENT S ADDKESS. 



bility of a focus of disturbance not accurately at a point, but 

 rather along a short line. 



The exceedingly delicate instruments of various kinds which 

 modern science makes use of have brought to light the fact 

 that, even in what we are accustomed to think of as undisturbed 

 countries, the earth's crust is in an almost constant state of 

 tremor, and it is possible that some of these minor vibrations 

 may be due to other than strictly volcanic causes, — such, for 

 instance, as sudden fractures and slippings of rocks, or the 

 collapse of subterranean cavities, such as are very likely to be 

 produced by the secular cooling and contraction of the globe. 

 It is a remarkable fact, but one that appears to be borne out by 

 the examination of a large number of records of earthquakes, 

 that these are more frequent in winter than in summer, and 

 the local belief is that Stromboli is more active in stormy 

 weather, when the barometer is low, than at other times. It 

 would seem as if even such relatively small changes of pressure 

 as those of the atmosphere on the earth's surface are responded 

 to by the solid crust ; how much move are such responses likely 

 where great masses of material are being piled along the margin 

 of an ocean area — the land area being at the same time relieved 

 from the pressure. 



The linear manner which volcanic phenomena so much 

 affect was strikingly shown in the other great phenomenon of 

 the year, the terrific explosion of Krakatoa, in the Straits of 

 Sunda. Java has always been noted for the altogether excep- 

 tional violence of its volcanic eruptions. It needs but to recall 

 those of Papandayang, Sumbawa, and Tomboro, to find parallels 

 to that which so much aroused our interest in September last. 

 The manner of them all is very similar. A momitain known 

 to be a volcano is suddenly either completely blown away or 

 enormously truncated. Little or no lava flows, but immense 

 tracts of country are buried in ashes. Torrents of rain cause 

 floods, which sweep away the terrified survivors of the explosion, 

 and complete the ruin by enabling the ashes to set hard like 

 cement. In addition to all this, mighty waves are raised in 



