MINING IN MOUNTAIN REGIONS 515 



Sometimes earthquakes are followed by terrible fires 

 which cannot be extinguished on account of the disarrange- 

 ment of the water supply. This was the case in the San 

 Francisco earthquake. With the care taken in rebuilding 



SAN FRANCISCO FIRE 



The direct damage to property and loss of life by earthquake in 1906 was 

 insignificant. The disarrangement of the water supply made possible 

 one of the greatest conflagrations in history. Extraordinary precautions 

 were taken in relaying the water mains of the risen city. 



that city and in laying its water-mains, it is unlikely that 

 any such disaster could ever follow another earthquake of 

 the same sort. 



Mining in Mountain Regions. When rocks are folded 

 and crushed, in forming mountains, heat is generated, and 

 heated water under pressure acts upon the components of 

 the rocks and dissolves some of their minerals, which ac- 

 cumulate in cracks and crevices called veins. When the over- 

 lying beds have been worn away, these mineral veins, formed 



