CHAPTER LXVIII 



THE THERMOMETER 



THE story of the gunner," Jules remarked, 

 "ended very differently from what one ex- 

 pected at the beginning. Just when one thinks the 

 two travelers are done for, it turns out nothing 

 more serious is in question than the roasting of two 

 fowls. A shiver of fear seizes you when the man 

 climbs the ladder with the cutlass between his teeth ; 

 the next minute you are laughing. That is a very 

 amusing story; but it has turned us aside from the 

 earthquakes. You have not told us yet the cause 

 of these terrible movements of the ground." 



"If that interests you," replied his uncle, "let us 

 talk about it a little. I will tell you first that the 

 farther you descend into the earth, the hotter it 

 becomes. Excavations made by man for obtaining 

 various minerals give us valuable information on 

 this subject. The deeper they go, the hotter it is. 

 For every thirty meters of depth there is an in- 

 crease of one degree in temperature." 



"I don't know very well what a degree is," said 

 Jules. 



"And I don't know anything about it," confessed 

 Emile. 



"Let us begin with that; if not, it would be im- 

 possible for you to understand. In my room you 



334 



