THE PRODROMUS 235 



winds be air expanded by heat or whether different fluids of 

 P. 35. the air made violent by collision produced them. 



3. Ill-smelling exhalations, fiery or frigid ebullitions, and so 

 on. And there is no longer any doubt of the fact that cold and 

 dry places boil up without any trace of heat whenever water is 

 poured upon them ; that a hot spring issues by the side of a 

 very cold spring; that in consequence of an earthquake a hot 

 spring may be turned into a cold spring, and rivers change their 

 course ; that valleys shut in on all sides discharge their gathered 

 rain water into lower places ; that rivers gliding underneath the 

 earth's surface are in places returned to the light of day ; that in 

 laying foundations architects sometimes lose all their labor 

 when they encounter a quicksand, as it is called ; ^ that in cer- 

 tain places on digging wells water is at first found near the sur- 

 face of the ground, then after digging to the depth of several 

 yards new waters are discovered which at first, on the opening 

 of a passage-way, leap forth beyond the height of the water 

 already found ; that whole fields with trees and buildings sink 

 gradually, or are engulfed suddenly, and hence vast lakes now 

 exist where once stood cities ; that a plain is a source of danger 

 to its inhabitants from catastrophes of this kind unless they 

 have made themselves sure about its foundation of rock; that 

 abysses emitting a deadly gas are sometimes found which are 

 again stopped up when a number of bodies have been cast into 

 them. 



THE ORIGIN OF VARIEGATED STONES AND THE REPOSITORIES OF 



MINERALS 



The same alteration in the position of strata has given rise 

 to variegated stones of every kind, and at the same time 

 p. 36. afforded a repository for most minerals, whether the deposition 

 took place in the cracks of the strata, or in those fissures which 

 were, in respect to matter, dry but not yet hard, either between 

 the layers or in their clefts ; or in the interstices between the 

 upper and the lower strata after the falling of lower strata ; or 

 in the places left empty by the decomposition of bodies therein 

 contained. Whence it can be shown : 



I. That on the very slightest foundation, nay, apparently on 



1 arena viva, ' living sand,' is Steno's phrase. 



