[ H3 ] , 



■between thofe two fpecies of calcareous ftone, it will be fufficient 

 to call the firft the fhelly calcareous, and the fecond the pure 

 calcareous. The fhelly calcareous ftone, though alway laid on 

 the fkte, is not the only ftone which occupies that place ; for wc 

 fee that the lower part of the mountains, to the fouth of 

 Oughterard, exhibits alternate layers of quartz and flate, and 

 that their fummits confift entirely of quartz. The fame obfer- 

 vation is to be made on St. Etienne en forez in France. On the 

 fide of Mount Bilat, a heap of flate is to be feen, called Roche 

 Coupee, which rifes to the elevation of from 60 to 8d feet on 

 the flaty top of the mountain, and exhibits very diftind beds 

 like thofe of Mahiramore. The black mountains in lower Brittany 

 contain fuch beds of quartz as form in themfelves mountains over 

 the flate. Mr. Patrine, a french naturalift, who went to fee the 

 mines of Siberia, aflures us that he has feen fome exadlly like 

 them in the north. , ' ' 



The mountains which furround the bay of Dublin on the 

 north are very interefting ; for upon examination they are found 

 to confift of flate, in which confiderable beds of quartz predo- 

 minate, at one time very pure, and at other times more or lefs 

 argillaceous, but generally like what the French mineralogifts call 

 petrofilex. The mountains bordering the fea on the coaft of 

 Holyhead, facing Dublin, are abfolutely of the fame nature with 

 thofe laft mentioned ; but as it is not our objed to compofe a 



theory 



