Mineralogy of Sky, S 



errors of those who have preceded me, I have rarely if ever at- 

 tempted to draw such general conclusions. My chief endeavour 

 has been to reduce questions of this nature to a narrow compass, 

 where the limits admitted of contraction ; and where any thing has 

 appeared uncertain or contradictory, to put those uncertainties and 

 contradictions in the clearest light, that future observers might di- 

 rect their attention to those points-which most stand in need ot 

 elucidation. 



To place the subjects which have occurred in the examination of 

 Sky, in an order as nearly as possible both conducive to topogra-- 

 phical clearness and geological elucidation, I have varied the order 

 of description as circumstances dictated. When the structure was 

 simple, and the geographical details corresponded, the task has been 

 easy to the writer, and will be easy to the reader. When it has 

 been otherwise, I have attempted as far as possible to reconcile 

 these claims ; while In the greater number of instances, where the 

 intricacy of the geological structure and the scattered disposition of 

 the materials over a large extent of surface have prevented all pos- 

 sibility of reconciliation, I have been obliged in some measure to 

 divide the subject with a reference to both these objects, preferring 

 to incur the charge of prolixity rather than that of obscurity. I 

 shall therefore commence by giving a general sketch of the se- 

 veral rocks which form the island, noting their geographical posi- 

 tions as accurately as circumstances permit j after which I shall 

 attempt to trace their geological arrangement, entering more largely 

 on those details which lead either to useful doubts or probable elu^ 

 cidation. 



The want of accurate geodesic operations has left the form, di- 

 mensions, and position of Sky, as yet desiderata in British geo- 

 graphy, an inconvenience however, much less in a geological view 



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