( 8o ) 



ample. He has remarked that a fprhig of 

 warm water at Laugarnes, in Iceland, when 

 It iflues bubbling from the earth, leaves no 

 fediment of any kind, but depofits it at the 

 bottom of a channel by flowing through 

 which it becomes cooler: and this fediment is 

 truly zeolitic, as has been proved by che- 

 mical examination *. The nature of this facft 

 he fatisfadorily explains as follows : " While 

 the water is very warm, it holds the zeolitic 

 matter in diflblution ; but, afterwards, be- 

 coming cold, can no longer fupport it, fo 

 that it precipitates and forms this ftaladtical 

 concretion. This excellent obfervation will 

 account for the frequency of zeolites in 

 many volcanos, fmce the water, whether fait 

 or frefh, being ftrongly heated by the fub- 

 terraneous lires, diflblves the zeolitic fub- 

 ftances, which it afterwards depofits within 

 the lava, where they cryftallize, or remain 

 amorphous, according to circumftances. 



When the traveller has arrived at the 

 fnmmit of the Monte della Stufe, he has 



^ Opufc. Vol. III. 



reached. 



