Mineralogy of Sky, 47 



described, and evidently in a higher situation : it is a calcareous 

 sandstone, and bears a precise resemblance to that which consti- 

 tutes the whole of the eastern side of Strathaird. Now as no sand- 

 stone of this description is found among the lower beds, and as 

 we have clearly traced the order of those from the mica slate to 

 this point, I think that we need not hesitate in placing the sand- 

 stone of Strathaird in the situation which I claim for it, the last in 

 the series of the secondary strata. However that shall be de- 

 termined, I must proceed to describe it. It is to be seen reaching 

 from the termination of the trap on the western side of the pro- 

 montory, round the point of Aird to nearly the upper end of 

 Loch Slapin, preserving a great evenness of direction and con- 

 sistency of character throughout this space. I have called it in 

 general a sandstone, although it will be seen that it also contains 

 beds of limestone, but in small number and quantity. The po- 

 sition of the leading line of these beds is so generally horizontal 

 that it is never found to vary five degrees, and that variation is 

 so gradual that it will often pass without notice : but it is at- 

 tended with a disposition so remarkable, that I think it neces- 

 sary to point it out, and as it is difficult to render it intelligible 

 in words, I have added a diagram* for illustration. Each 

 bed seems compounded of two parts, the one a single horizontal 

 lamina, and the other a series of inclined ones, or, there is a re- 

 gular alternation of a set of inclined laminae with one horizontal 

 one. These are perfectly defined, since the intervals are deeply 

 channelled by the weather, the whole having the aspect of some 

 of the carved ornaments of Saxon architecture. This appearance 

 gives on a first view the impression as of a regular series of beds, 

 alternating with each other, of which the one is horizontal, and 



* PI. 4. fig. 1. 



