48 On the Coal-field of Sutherland. 



is the last subject connected with the history of these strata yet 

 remaining to be noticed. 



This inclination is exceedingly irregular and inconsistent. 

 At the coal works at Brora, it is about 12'^, or varies from 10° 

 to 15° ; dipping to the south-east. Here I must remark, they 

 lie at some distance from the foot of the hills. Near the 

 northern parts of the field, the inclination varies from 20° even 

 to 60° and 70° ; and in some places, they are even vertical. In 

 one or two situations, I observed them reversed in contact, 

 although no intervening veins were present. It seems also to 

 be a sort of general rule, that as they approach the hills, the 

 angle of inclination increases ; although exceptions to this law 

 occur. If the dip is not invariably to the south-eastward, that 

 must still be considered the predominant one ; a circumstance 

 which might be expected from the position of this field with 

 respect to the hills. The exceptions, however, which occur, 

 are neither unfrequent nor trifling ; as the dips are often found 

 to be north or south, and at every possible angle, even in a 

 very narrow space. 



Before proceeding further in the history of these strata I 

 must interpose a few remarks, as a continuation of the same 

 fact which forms a remarkable circumstance in the first portion 

 of this paper ; the granite is succeeded by what will presently 

 be seen to be a very remote portion of the secondary strata 

 and without the intervention of any primary strata. By the 

 manner in which these strata succeed to the granite, it is plain 

 that the order is not entire throughout; but that different 

 members of the series, where it is complete, come into contact 

 with the fundamental rock. As it has also been already in- 

 ferred that this granite is not posterior to the strata, but that 

 they have been deposited on that rock, it follows from the cir- 

 cumstances stated in the preceding paragraph, that the inferior 

 strata have, in certain parts, ceased in succession to be depo- 

 sited, thus admitting the upper members to come into contact 

 with the fundamental rock. This occurrence is, however, so 

 common in other cases where secondary strata occupy the 

 geological situations commonly called basins, that it needs 

 excite no surprise. The present fact is, however, as yet a 

 solitary occurrence ; it is the only instance known, in which 

 strata so high in the usual order of succession, are found ia 



