THE SCHISTOSE ISLES. 283 



Chlorite series, GS formation, a term necessary to discrimi- 

 nate it from the series of micaceous schist with which 

 it has hitherto been confounded. Its character will be 

 found sufficiently remarkable, and sufficiently distinct from 

 that of the micaceous schists throughout Scotland, to 

 justify this new arrangement. 



If a line be drawn nearly parallel to the southern shore 

 of the eastern branch of Loch Fine, at a small distance 

 from the sea, and prolonged to the western coast of 

 Cantyre, it will represent, with an accuracy sufficient for 

 the present purpose, the south-eastern boundary of this 

 series ; that boundary being coincident with the bearing of 

 the strata. The corresponding parallel boundary to the 

 north-west, will be found in the island of Shuna and on 

 the adjoining mainland; the extreme visible portion of the 

 series being the grey ridge of Luing and Seil. This 

 boundary is rendered imperfect by the occurrence of the 

 trap of Lorn, which overwhelms the chlorite series, together 

 with the conterminous mass of clay slate that occupies the 

 Slate isles aud the adjoining continent; the indications of 

 the junction of these being barely visible in the proximity 

 of Slmna to Luing, in the grey ridge of the latter, and in 

 a point on the mainland opposite to Torsa. It is evident 

 that the boundary to the south-westward, across the strata, 

 is the sea ; while the corresponding one, to the north-east 

 is, like the former, obscured ; partly by the soil of the 

 interior district of Argyllshire, to which the strata are 

 prolonged, and partly by the great tract of porphyry which 

 covers the stratified rocks in this quarter. Such is the 

 geographical extent of that portion of this series to which 

 the islands in question belong : it would exceed the limits 

 of this investigation to pursue it further into the interior of 

 Scotland, where it also occurs in a distinct manner. 



In examining the lateral boundaries of this series, no- 

 thing can be added to the account just given of the north- 

 western limit : but it is apparent that the termination 

 is here definite as far as it is visible ; the only vacillation 



