334 SKY. GEOLOGY. SECONDARY STRATA. 



for want of others more satisfactory, it is marked in 

 the map as including a roundish low hill of which the 

 house of Ord is the centre. 



The irregularity of its position is considerable, but in 

 this respect it only partakes of the general disorder that 

 equally attends the sandstone on each side. At its southern 

 extremity the beds are even, and follow the general direc- 

 tion of all the strata, while they also dip to the westward. 

 This regularity continues for about half the space through 

 which it is visible. It then becomes so confused that 

 it is difficult to discover a predominant tendency, imme- 

 diately after which it is found lying in vertical beds and 

 tending to the N. N. E. These acquire by degrees a 

 northern direction with a slight western dip; when the 

 limestone totally ceases and is followed by the white quartz 

 rock formerly described, in a parallel order ; but after a dis- 

 continuity of all rock occasioned by a narrow valley which 

 on each side cuts off the hill of Ord from the adjoining land. 

 Although the junction therefore can no where be seen, 

 there is, in the relative positions of the different rocks, 

 sufficient reason for concluding that this mass is superior 

 to the sandstone series, and consequently, that, however 

 irregular in structure, it is one of the lowest portions of 

 the series of Strath. 



Whatever the irregularity may be, it is still always 

 disposed in beds of greater or less thickness, which, on 

 weathering, present much of the external aspect of the 

 unstratified limestone formerly described. It is either 

 of a dark lead blue, or a pale grey colour, sometimes 

 earthy, now and then assuming a crystalline texture, and 

 often extremely hard, with a clean and sharp splintery 

 fracture approaching to the conchoidal. It is distinguished 

 from all the limestone already described by the great 

 quantity of siliceous substances it contains. These are 

 either disposed in veins or in irregular nodules ; in some 

 cases so far predominating that the calcareous rock is 

 nearly excluded, and in a few indeed entirely superseding- 



