18 IONA. GEOLOGY. 



streaks and drops of oil. In many places it has a 

 schistose tendency, more particularly where it approaches 

 to the schist in which it lies. Here also it becomes mag- 

 nesian, and passes by irregular gradations into a steati- 

 tical calcareous schist. It contains in some parts distinct 

 leaves of translucent schistose steatite having an ap- 

 pearance and colour much like that of half frozen olive 

 oil. Dark green foliated steatite is also found in it, 

 accompanied by pale yellowish green and by dark green 

 noble serpentine; which, when detached and rounded on 

 the shore, are well known to the visitors of lona, and 

 have been often mistaken for jade. I observed only one 

 specimen containing asbestos. 



At the points of junction with the schist it is partially 

 mixed with and passes into it, as the limestones which 

 lie in mica slate are known to do, by a sort of alternating 

 gradation. But it presents also a phenomenon scarcely 

 to be expected here ; a contortion, by which it is irregu- 

 larly drawn out, and waved together with the accompa- 

 nying schist ; the parts being involved and entangled 

 in a confused manner*. As the beds of gneiss have all 

 suffered contortion and derangement, there is, however, 

 no reason why the accompanying limestone should be 

 exempt, be the cause what it mayf. 



The beds of rock which succeed in proceeding north- 

 ward, appear to be generally placed in a vertical direction, 

 but in a very irregular manner and with very little 



* PI. II. fig. 5. 



f In the posthumous papers of the late Doctor Walker, it is said, 

 that green serpentine is found on the shore at the south side of lona, 

 and that it may be quarried to any extent. Though prepared to look 

 for it I did not find any other serpentine but that which is con- 

 tained in the marble. Had it been small in quantity, I might perhaps 

 have overlooked it; as among a wilderness of grey rocks of which the 

 external aspect is alike, it is scarcely possible to examine the com- 

 position of every portion ; but I can hardly conceive that any extensive 

 rocks of this nature can exist here. I am more inclined to imagine 

 some error in the statement. 



