1857.] GEIKIE SKYE. 23 



later secondary or earlier tertiary epochs ; and I am much inclined 

 to think that some of the later felspathic ashes and basalts which 

 dot the mainland, together perhaps with not a few of the great 

 parallel faults and dykes, may belong to this volcanic era. A 

 thorough examination of these islands cannot fail, therefore, to elicit 

 much truth as to some obscure points in the physical history of 

 Scotland. 



Of the geology of Strath, however, there is one branch that 

 seems to be complete in itself, whereon we can expect little light 

 to be thrown from other districts. I allude to what is certainly 

 its most characteristic feature — the metamorphism of the lias- 

 limestone. Strath may be surpassed by other localities among the 

 Western Islands in the preservation and number of its organic re- 

 mains ; but I despair of meeting with a more striking example of 

 metamorphism. The igneous rocks of this parish, with their va- 

 rieties of kind and form, and their effects on the surrounding strata, 

 impart to it an interest all its own. 



Notes to the Map and Sections : Plate I. 



The accompanying Map has been taken partly from that of Dr. 

 Macculloch, partly from the Charts of the Admiralty Survey, of 

 which a tracing was kindly sent me by Captain Wood, R.N., Kyle, 

 and partly from bearings with the azimuth-compass. It is far from 

 being accurate ; yet the errors are not probably so material as to 

 affect to any considerable extent the general bearings of the geolo- 

 gical lines. 



With regard to the geological part of the Map, there is but one re- 

 mark needed here. The irregular bulging hill of Creag an fithick, 

 south of Beinn Dhearg, is coloured (in the original) like the syenite, but 

 of a fainter tint. The rock has puzzled me not a little. Sometimes 

 it seemed like an earthy greenstone, sometimes like a felspathic por- 

 phyry ; at some points it assumed many of the characteristics of an 

 ash or tufa, with fragments of altered shale ; at others it approached 

 in texture and general appearance the syenite of the contiguous hills. 

 It is likely that there may be several kinds of igneous rock in the 

 series of lumpy knolls from Kilbride north-eastward, but I was 

 unable to separate them out, and I have coloured the whole as one 

 mass. It is by no means easy to ascertain to what age these rocks 

 belong ; they seem to have come up in the rent formed by the dis- 

 ruptive syenite of Beinn Dhearg, and to have flowed over atop. But 

 it would be rash at present to hazard any conjecture regarding them. 



[The lines of sections, with roman numerals, on the Map, fig. 1, 

 refer to the MS. Sections.] 



The Sections are drawn on the scale of 1 inch to the mile, except 

 with regard to the height above the sea-level, which in most cases 

 has had to be exaggerated. [In fig. 8 the syenite has been lessened 

 in height.] The upper horizontal line in each of the Sections marks 

 the sea-level, and the space between that line and the lower one re- 

 presents a thousand feet of vertical depth. 



