Geological Obfervations. 39$ 



fift putrefaction moft are frequently found 

 petrified ; fuch as {hells and the harder fpe- 

 cies of woods : on the contrary, thofe that 

 are apteft to putrefy are rarely found petrified, 

 as fifh, and the fofter parts of animals, &c. 



^aiy. That they are moft commonly found 

 in ftrata of marl, chalk, lime-ftone or clay, 

 feldom in fand-ftone, ftill more rarely in 

 gypfum, but never in gneifs, granite, ba- 

 faltes or fhoerl j but they fometimes occur 

 among pyrites, and ores of iron, copper and 

 filver, and almoft always confift of that fpe- 

 cies of earth, ftone, or other mineral that 

 furrounds them, fometimes of filex, agate, 

 or carnelian, 



4 thjy - That they are found in climates where 

 their originals could not have exifted, 



thofe found in flate or clay are 

 comprefled and flattened. 



Of Metallic Ores. 



Iron ore is the only one that forms intire 

 mountains , all other ores form but an in- 

 confiderable part of the mountain in which 

 they are found, 



Ores either run parallel to the ftony ftrata, 



or 



