THE KING'S MIRROR 17 



imagined that somewhere there were " certain cavern- 

 like abysses, which now swallow up the water, and now 

 spew it forth again."* The author of the Speculum has 

 no doubts on the subject: he believes that the tides are 

 due to the waxing and waning of the moon.f 



In his discussion of the volcanic fires of Iceland he 

 shows that on this subject he was completely under the 

 influence of medieval conceptions. He has heard that 

 Gregory the Great believed that the volcanic eruptions 

 in Sicily have their origins in the infernal regions. Our 

 author is inclined to question, however, that there is 

 anything supernatural about the eruptions of Mount 

 Etna; but he is quite sure that the volcanic fires of Ice- 

 land rise from the places of pain. The fires of Sicily are 

 living fires, inasmuch as they devour living materials, 

 such as wood and earth; those of Iceland, on the other 

 hand, consume nothing living but only dead matter 

 like rock. And he therefore concludes that these fires 

 must have their origin in the realms of death. { 



The author has a suspicion that earthquakes may be 

 due to volcanic action, but he offers another explana- 

 tion, though he does not give it as his own belief. Down 

 in the bowels of the earth there is probably a large num- 

 ber of caverns and empty passages. " At times it may 

 happen that these passages and cavities will be so com- 

 pletely packed with air either by the winds or by the 

 power of the roaring breakers, that the pressure of the 

 blast cannot be confined, and this may be the origin of 

 those great earthquakes that occur in that country." 



* Alexander Neckam, De Naturis Rerum, 138. f C. vi. 



J C. xiii. Ibid. 



