256 



PRINCIPLES OF STRATIGRAPHY 



ing kaolinized in a high degree, exhibited considerable blunting of 

 their angles. The chlorite flakes were generally rounded, though 

 with frayed, irregular edges, the muscovite and biotite were some- 

 what rounded on their prominent angles, but generally of irregular 

 outline. The hornblende and garnets were angular, as was also the 

 zircon, though showing occasionally ground-glass surfaces. Mackie 

 concludes that these sands had traveled not less than 70 miles. 



A specimen of sand from the seashore, midway between Lossie- 

 mouth and Covesea on the south coast of the Moray Firth, gave 

 Mackie the following results : 



Table sliowing rounding of sands of Moray Firth. 



Mineral Particles 



Hornblende 



Kyanite 



Biotite 



Opaque iron ore . 



Chlorite 



Muscovite 



Quartz** 



Feldspar** 



Average 

 round- 

 ing* 



1-5 



1-5 

 1.8 

 2 .0 

 2 .0 

 2.2 



1-7 

 2. 1 



Average rour;ding represented by . 



A sample from the sand dunes of Culbin, in the same region, 

 gave the following : 



Table shozving rounding of sands of Culbin dunes. 



Mineral Particles 



Staurolite 



Kyanite 



Garnet 



Hornblende 



1 ourmaline 



Opaque iron ore . 



Sphene 



Zircon 



Feldspar 



Quartz 



No. 

 ob- 

 served 



2 



2 



45 



5 



13 

 10 



9 

 7 



16 

 16 



Rounded 



13 

 3 



7 



10 

 6 



Sub- 

 angu- 

 lar 



I 



14 

 I 



4 

 3 



Angular 



Average 

 round- 

 ing 



1 .0 

 1-5 

 1-9 



2.4 



2.5 

 2.7 

 2.8 

 30 

 2.6 

 2.3 



Average rou nding represented by 2.27 



* Obtained by counting 3 for a round, 2 for a subangular, and i for an angular 

 particle and dividing the sum by the number of particles in each group. 



* * A proportion of these evidently derived from the sandstones of the coast. 



