( i^S ) 



This ingenious theory is not only contra- 

 dided by the obfervation made above, but ap- 

 pears to me not to accord with the ufual ope- 

 rations of Nature. Were it well founded, I 

 can perceive no reafon why the fhoerls in 

 lavas fhould not re-appear after they have 

 been fufed within them in the furnace, 

 and, being removed into a cold place, have 

 acquired their former hardnefs. But though 

 I made experiments with fire on fome 

 thoufands of pieces of lava, not one of 

 them re-produced its fhoerls, though many 

 were continued a long time in a ftate of 

 fufion, and afterwards fufFered quietly and 

 flowly to cool and confolidate ; v;hich two 

 circumftances are known to favour the 

 formation of cryftallizations. Shoerls were, 

 indeed, fometimes found in the lavas, after 

 fufion, when cooled and hardened ; but thefe 

 had proved refradory to the fire ; as appear- 

 ed on expofmg them again to the furnace 

 detached from the lava. 



The eleven pieces of primordial rock 

 M 3 broken 



