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The refpedtive fituations of thefe different fubftances are fk> 

 gularly perfpicuous at the bridge of Oughterard. The cafcade 

 which the river forms in that place, feparates the granite from 

 the calcareous country. The precipitate motion of the torrent 

 has ftripped and dug up the foil to fuch a degree, as to expofe each 

 layer or ftratum of the rock, and fhew them arranged in a 

 fymmetrical order, feldom to be met with in the irregularities of 

 nature. The grotto which has been conflrudted near that cafcade, 

 is cut into the very fpace that divides thefe two fyftems. Here 

 one may fee three or four beds of flate, which are laid immedi- 

 ately ove. the granite, and which are covered over with calca- 

 reous layers, perfedly parallel to them. Thus we learn the order 

 in which the operations of nature were performed. By this fort 

 of obfervation we are taught to know that the granite was the 

 ground-work of the globe ; that the flate was afterwards formed 

 and laid over it ; and that finally the calcareous ftone, the moft 

 modern of all, was laid over the latter. We muft here remark, 

 that the calcareous ftone we are now talking of, is that wherein 

 one meets an infinity of fhells. As to that fpecies of it which is 

 abfolutely pure, without the apparent remains of fea-animals, 

 fuch as are to be feen in the mountains of Glan, and which are 

 alfo to be feen in the very high mountains of the Alps, it is 

 not as yet decided whether we are to confider thofe as contem- 

 porary to the granite or to the flate, or whether their origin be not 

 of the fame date with the preceding clafs. In order to difiinguifh 



between 



