288 REACTION OF THE INTERIOR OF THE EARTH 



pourings of lava, forming connected masses, and What he 

 terms a stream of stones, consisting of glowing fragments, 

 for the most part angular, emitted in quick succession : 

 " There was heard the crashing sound of the hurled-up 

 stones falling on the declivity and rolling down, looking 

 like points of fire, following each other either in line 

 or without order." I desire to fix attention on the very 

 different modes in which the appearance of fire on the 

 slope of a volcano may be produced, because in the dis- 

 cussion on the maximum angle of fall of streams of lava, 

 streams of glowing stones or fragments of rock (masses 

 of scoriae) have sometimes been confounded with conti- 

 nuous lava-currents. 



As much has recently been said respecting the 

 rarity, or supposed entire absence, of lava-streams in 

 Java a problem important in relation to the internal 

 constitution of volcanoes, and which I venture to add 

 has not been treated with sufficient earnestness, the 

 present appears to me a suitable opportunity for con- 

 sidering the question in a more general point of view. 

 Although it is very probable that in a group or a series 

 of volcanoes all the members will stand in certain 

 common relations to the common hearth (the molten 

 interior), yet each individual presents peculiar physical 

 and chemical processes in respect to strength and 

 frequency of action, to degree and form of fluidity, 

 and to diversity of products peculiarities not to be 

 explained by differences of form or of elevation above 

 the present surface of the sea. The colossal Sangay is as 

 uninterrupted in eruption as the low Stromboli. Of two 

 volcanoes near to each other, one sends forth pumice 

 without obsidian, and the other emits both together; 



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