Il5 MINERALOGICAL QUERIES. 



of Eigg, is one of the most magnificent assemblages 

 of natural columns, hitherto noticed by any natu- 

 ralist. The rock of which these columns are 

 composed is porphyritic, with a base intermediate 

 between basalt and pitchstone. It appears to be- 

 long to the newest flcetz-trap formation. 



24. What are the rocks of which the island of 

 StafFa is composed, and what are their geo- 

 gnostic relations ? 



The columnar distinct concretions, or pillars of 

 StafFa, are said to rest upon trap- tuff ; but the true 

 nature of these pillars has not been hitherto dis- 

 tinctly ascertained. 



25. Is the porphyry of the isle of Raasay^ 

 porphyritic claystone, and porphyry-slate ? 



26. What are the geognostic relations of the 

 tremolite and zoisite of Glenelg in Inver- 



, ness- shire ? 



27. Does the sandstone of the Shetland islands 

 belong exclusively to the oldest coal forma- 

 tion, or do different sandstone formations oc- 

 cur there * ? 



* The Reverend Mr Fleming, in a paper read before 

 the Society, has rendered it probable that the sandstone 

 of Shetland belongs to the oldest coal formation. 



