374 GEOLOGICAL APPEARANCES 



both belong. Or Hutton's chief error in describing Glen Tilt is, 

 that of stating the mountain on the northern side of the valley to con- 

 sist of red granite. JHe was probably led to this false inference, by 

 what he saw in the deep cut made by the Criny, and by loose 

 blocks near its entrance into Glen Tilt. 



Note D, Parag. 139. 



About sixty yards above the junction of the Chlochan, there are 

 seen in the bed of the Tilt, strata of a white granular limestone, high- 

 ly crystallised, interstratified with, and penetrated by, mica and felspar, 

 and containing pyrites. The mica gives it a slaty fracture in the 

 large. The greater facility with which the carbonate of lime is worn 

 away by the water, has caused the felspar to stand up in some places, 

 in a rough and porous crust, on the surface of the rock. The position 

 of these strata differs much from that which is most common in Glen 

 Tilt ; for their stretch is N. 150° E., and their dip north-east at an 

 angle of 41°. Those on the eastern bank of the river are cut by red 

 veins, either of felspar or sienite*. 



A hundred yards farther up the stream, I again fell in with the 

 dark-grey aggregate. 



A hundred and fifty yards higher, there arc strata in the fare of 

 the hill above the southern bank, which seem to be. limestone. They 

 dip to the eastward into the face of the hill, but are much bent. 



In the course of another hundred yards, the dark-grey aggregate 

 again occurs in the bed of the river. 



^A hundred and fifty yards farther up, there is mica-slate, stretch- 

 in^ N. 128° E., and dipping to the north-east at an angle of 45°. 



The stretch and dip of the strata, where distinct, continues much 

 the same for a hundred and fifty yards, when there appears mica- 

 slate,, 



* This is one of the exceptions alluded to in parag. 110- 



