( '98 ) 



the petrofilex ; which two flones, according 

 to the obfervations of M. Dolomieu, form 

 fome of the Egyptian bafaltes, which are a 

 work of the waters. Thefe two agents, 

 fire and water, are not, in fa£t, fo different 

 in their aCcion as we might at firft be in- 

 clined to imagine. The prifmatic figure in 

 the humid way arifes in the foft earth by 

 the evaporation of the water ; in confe- 

 quence of which the parts dry, contrail 

 their volume, and fplit into polygonal 

 pieces. The fame phenomenon may be 

 remarked in margaceous earths, imbued 

 with water, and expofed to the ventilation 

 of the air ; and I have frequently feen the 

 mud of rivers, when dried in the fun, in 

 fummer, to make pottery-ware, divide, 

 when it became dry, into fmall polyedrous 

 tablets. Similar configurations are pro- 

 duced in different lavas by the congelation 

 and contraction that take place by the pri-. 

 vation of the fire which held them in a 

 flate of fluidity. 



It appears to me, therefore, that the dlf- 



pute 



