On the Coal' field of Sutherland, 49 



contact with that rock which is the lowest of all, whether se- 

 condary or primary. 



The last general consideration in this case relates to the 

 disturbance of the coal strata in this field, which 1 have shown 

 to be considerable. It is undoubtedly a common occurrence 

 everywhere ; yet, as a great variety of substances, reaching to 

 a great depth, are in all such cases found beneath those strata, 

 the nature or the places of the cause which have led to thera 

 are entirely out of the reach of conjecture. Here, the lowest 

 rock, the granite, is immediately in contact with the secondary 

 strata J and if these disturbances have been produced by partial 

 elevations, or subsidencies in the foundation, it is in that rock 

 that they must be sought. In other cases, among the pri- 

 mary strata, where it seems probable that the disturbances of 

 these have been produced by changes in the condition of the 

 subjacent granite, that probability rests chiefly on the intrusion 

 of this substance in the forms of veins, on its peculiar and 

 irregular obliquity to the strata at the places of mutual con- 

 tact, and on circumstances which have so often been discussed 

 that it is unnecessary to repeat them. But here no veins 

 have been discovered; and it seems, on the contrary, pro- 

 bable, that the secondary strata in question have been de- 

 posited originally on the solid granite, whatever posterior, 

 changes they may have undergone. The granite, therefore, 

 not having been protruded in a fluid state beneath them, what- 

 ever changes of figure it may have undergone capable of pro- 

 ducing the disturbance of the strata, must have been effected 

 by causes acting at a greater depth within the earth, and suf- 

 ficiently powerful to alter the form of the solid rock above, 

 together with the angles or inclinations of the strata that lie 

 upon it. I need only add, that these phenomena, on this 

 side of the granite mass, are ample evidences of what, in the 

 former part of this paper, where the sandstone alone is con- 

 cerned, might have appeared conjectural. ■, 



I shall conclude these general remarks on this ** coal-field," 

 with the following observation. These secondary strata con- 

 tain fragments of other secondary strata of similar character, 

 imbedded in the base. These also are not of the nature of 

 local conglomerates, or they are not such fragmented rocks as 

 are found on the surfaces merely, or at the junctions of dis- 



JAN.— MARCH, 1830. E 



