Mineralogy of Sky. 49 



jnuch in quantity that the compound would sometimes be called a 

 calcareous sandstone, while at others it would be described as a si- 

 liceous limestone. In the latter cases it is often dark-brown, gray, 

 or even of a dark lead blue. The beds of mere limestone are 

 rare, and those which I observed lie towards its upper boundary ; 

 they are of considerable size immediately in the vicinity of the 

 Spar cave, which I described at the commencement of this paper. 

 I think they are much more generally granular than compact, 

 and some of them Indeed resemble an aggregate of rounded grains, 

 of the size of mustard seeds, not much differing from some of the 

 oolites, but more compacted, and generally containing, besides 

 these grains, crystallized platy particles. These strata are inter- 

 sected in a remarkable manner by trap veins ; but I shall defer 

 • the consideration of those to that which I conceive their proper 

 place, the last in the history of the rocks. 



The geographical chasm which interferes between this and the 

 remaining portions of v/hite sandstone found in Sky is such, the 

 want of accompanying strata so general, and the absence of cha- 

 racteristic indications in the internal composition so great, that I 

 feel quite unable to determine the nature and connections of these 

 detached portions. If any thing can be drawn from such indi- 

 cations as they present, they seem rather to prove that the sand- 

 stones which ?ire found at Portree and in the northern parts of the 

 island, appertain to strata different from those last described ; but 

 the remarks I have already made on the discontinuity of the lime- 

 Stone and the blue quartz rock, render me diffident in admitting 

 any evidence respecting continuity of stratification, or the reverse, 

 without access to proofs of a more decided nature. 



White sandstone is to be found in many places on the eastern 

 coast of the island, and is readily visible at Portree, where it alter- 

 . Vol. III. Q 



