544* MINERALOGY OF THE REI>HEAD, 



Another appearance of the same kind presented it-- 

 self to the north-east of the church of St Vigeans, 

 in an opening made in a field for the purpose of 

 obtaining gravel for the roads. Immediately un- 

 der the soil, there is a horizontal bed of gravely 

 containing thin layers of sand, resting upon the ex- 

 tremities of strata of coarse sand, dipping E. S. E. 

 at an angle of 24*. 



It is assumed as a first principle in the Hut- 

 tonian Theory, that all the mineral strata at their 

 formation, were deposited on a horizontal plane. 

 Loose materials, it is said, such as sand and gravel 

 subsiding at the bottom of the sea, and having 

 their interstices filled with water, possess a kind 

 of fluidity, and therefore would arrange them- 

 selves in horizontal layers. The figure pf the 

 lower beds deposited on an uneven surfiice, would 

 be affected by two causes, the nature of that sur- 

 face on the one hand, and the tendency to hori- 

 zontality on the other ; but the latter cause would 

 finally prevail. Whenever, therefore, we meet 

 with rocks disposed in layers quite parallel to one 

 another, we may rest assured, that the inequali- 

 ties of the bottom have had no effect, and that no 

 cause has interrupted the statical tendency But 

 the phenomena described above furnish evidence 

 by which this assumption may be successfully 

 resisted. Here are parallel strata of coarse sand, 



* Illustrations of th^ Huttonian Theory, p. 43. 



