238 



VULCAN1SM 



rise to mud-flows, which in some cases constitute a large part of 

 the final deposit. These mud-flows lodge chiefly on the lower 

 slopes of the cone or adjacent to its base. 



The common view that lava is melted rock, is hardly the correct one. At 

 any rate, it is at least equally correct to regard it as a solution of mineral matter 

 in mineral matter. A familiar illustration will show what is meant. If ice and 

 salt are mixed at a temperature of 30 F., the two form a liquid, though the tem- 

 perature is too low to melt either. We say the salt is dissolved, but it would be 



Fig. 230. The eruption cloud of Pelee, December 16, 1902. (Lacroix.) 



