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become aware of impending danger before man knows 

 that danger is at hand; though both will suffer the 

 same fate unless they escape from the vicinity. There 

 is often a rumbling noise accompanying the waves of 

 motion, which travel in an undulating manner, and 

 large chasms are opened in the locality of the severest 

 disturbance. Volcanic regions are more liable to earth- 

 quakes than others, owing to the infuriated condition 

 of the earth's interior at such places, and when erup- 

 tions take place they produce a great strain on the sur- 

 rounding country. The supposed cause of these dis- 

 turbances is mainly the heated condition of 

 the earth's interior, and the great strain and hard 

 swelling produced on the crust or surface, when the 

 mass is cooling. Thus the contraction and expansion 

 which takes place afterwards is held as the chief cause. 

 There are also other things which are considered as 

 secondary means in producing them. South America, 

 some parts of Europe, and other volcanic regions are 

 the main localities. 



In connection with this subject volcanoes should be 

 mentioned, as the two are to a certain entent linked 

 together. Tn general appearance they resemble com- 

 mon mountains, which they are, differing only by the 

 volcano having an open channel from the inside of the 

 earth to the outside, through which what is known as 

 lava is thrown or forced out. Volcanoes differ greatly 

 in size; also in the amount of matter thrown out. 

 They are divided into two classes, active and neutral. 

 The former are those which have a continual succession 

 of eruptions; the latter are those which seldom if ever 

 show signs of internal disturbance. Volcanoes which 



