132 THE ARCTURUS ADVENTURE 



each a foot or more in diameter, at the miniature 

 cinder cone which I reached. 



The fascinating thing about the sohd earth theory 

 is the action and reaction of heat and pressure on 

 rocks. If we penetrate the earth below the effect 

 of seasonal changes the temperature increases about 

 one degree in every sixty feet. Hence if the air at 

 the surface is 70° Fahrenheit, at a depth of a mile 

 it would be 158°. Carried to the center of the 

 earth, this would reach the exceedingly warm tem- 

 perature of about 350,000°! But the check to 

 this explanation of molten lava is that, with the 

 depth, pressure also increases from the earth's own 

 gravity, and pressure is an absolute inhibitor of 

 liquefaction. So as soon as we have gone deep 

 enough to obtain the requisite 2000° to 3000° of 

 heat necessary to melt rock, we automatically have 

 a pressure which prevents it. But when old earth 

 slips and shrinks, and surrounding hard rocks creep 

 and give room to uncountable threads of liquid 

 lava, and when the six mile zone of fracture beneath 

 our feet somehow achieves direct touch with that, 

 three or four times deeper, and the old mysterious 

 tidal gravity gets in its work, up comes the lava 

 to stir us mortals to our very souls. 



So this is the story of my Galapagos volcano, 

 which came to my consciousness with all the unex- 

 pectedness, and appealed to my enthusiasm and ap- 

 preciation with all the power, of a single marvel, 

 — at least that is what I thought as I steamed 

 slowly northward in late afternoon. The sunset 

 was directly behind it, and as the change was 



