434 SCALPA. GEOLOGY. 



The irregular boundary of the Sky limestone, which I 

 have generally attributed to the syenite, will thus also 

 in some measure appear to depend on 'the form of the 

 sandstone on which it has been deposited. 



I have added to the actual section of Scalpa, as far as it 

 can be made out from external examination, a speculative 

 one, * to explain the manner in which the sandstone and 

 limestone might be connected, on the view which I have 

 here held out ; and shall defer any further general remarks 

 to which the subject might give rise, till the remaining 

 islands connected with Sky have been described. I shall 

 only here add, that although the sandstone has been 

 traced to the mainland, the limestone does not there occur, 

 being entirely limited to the islands of this group. 



* Plate XIII. fig. 2. 



