152 HOXA. GEOLOGY. 



RONA* (WEST.) 



IT has been already remarked that this island was a 

 physical portion of the ridge of Heval, but it possesses 

 some peculiarities worthy of attention. It is about 

 600 feet in height, presenting in its higher parts the same 

 rocky aspect as Heval, and some low productive land 

 being found skirting the shore. It is much indented, 

 and exhibits to the east a broken face which seems, 

 like the rest of the eastern shore already described, 

 to consist of schist much disturbed and traversed by 

 trap veins. 



The same irregular mixture of gneiss, schist, and the 

 anomalous rock described above, are found forming its 

 upper parts ; both the mixture of the several rocks 

 and the gradation from the schist to the gneiss being 

 perhaps even more distinctly to be traced here than in 

 the ridge of Heval. Where there are opportunities of 

 observing this gradation, the change seems to be per- 

 formed by a gradual increase of the granitic ingredient, 

 the schistose parts communicating the laminar tendency. 

 There is thus produced a rock with a perfect resemblance 

 to gneiss, those portions which in more ordinary cases 

 are formed of mica or hornblende, consisting of argillaceous 

 schist. Reticulated trap veins are even more numerous here 

 than in Heval, and they add much to the extraordinary 

 appearance of this already obscure rock. Fa.wn coloured 

 as well as dark quartz is found in the gneiss, together 

 with felspar under the usual aspect which it possesses 

 in these islands, being splendent and nacreous. Besides 

 these, distinct beds of the same compact felspar de- 

 scribed in lona occur in different places, some of 



* Rona. Ron, a seal, Gaelic : Seal Island : a common appellation 



among the Western Wes. 



