1818.] Geological Transact ioyis-j Vols. III. and IV. 453 



Article XVI. 



Analyses of Books. 

 Transactions of the Geological Society. Vols. III. and IV. 



The interest and importance of these volumes demand a far 

 more extensive analysis of their contents than is consistent with 

 the plan of our journal. We trust, therefore, that our readers 

 will consider the following abstracts as intended rather to excite 

 than to satisfy their curiosity. 



1. Vol. III. — A Sketch of the Mineralogy of Sky. By J. 

 M'Culloch, M.D. F.L.S. &c. 



7. Vol. IV. — Corrections and Additions to the Mineralogy of 

 Sky. By the Same. 



The longitudinal extent of this island is from S.E. to N.W. 

 and its general figure is very irregular, being indented deeply on 

 every side by bays and sea-lochs. The south-eastern extremity 

 (consisting chiefly of the district of Sleat) is composed of gneiss, 

 passing by insensible gradations into chlorite state, and of 

 micaceous schistus. The beds rise to the N.W. at an angle 

 varying from 30° to 50°, or even more. At Loch na Daal they 

 pass into the sea, and may be observed to emerge at Glen Elg, 

 on the main land of Scotland, precisely in the prolongation, to 

 the N.E., of their line of run. To the N.W. of these beds, and 

 extending beyond them in a N.E. direction to the extremity of 

 the island, is a series of beds, which, where they touch the 

 gneiss, are nearly vertical ; they then become irregular, and, as 

 their distance from the gneiss increases, rise on the whole 

 towards the S.E. but with various local irregularities. This 

 series consists of red sandstone, of an indurated sandstone, 

 generally blue or grey, but occasionally brown, and sometimes 

 including grains of felspar, of greywacke schist, and, in one 

 place, of pure, compact quartz. The sandstones and schist 

 repeatedly alternate. The red sandstone is the predominant 

 member of this series, and in mineral characters corresponds 

 with the red sandstone, which in Scotland occupies an interme- 

 diate place between the primary rocks and those which contain 

 organic remains. Near the Point of Sleat, however, according 

 to Dr. M. this series of slate and of red sandstone passes by 

 degrees into a variety of gneiss, the former of these beds becom- 

 ing a green, glossy, chlorite slate, and the latter assuming the 

 appearance of a compact quartz containing grains of red felspar. 

 The newest beds of the sandstone just described, that is, those 

 which lie the furthest to the N.W. rise at an angle of not more 

 than 10°, and are covered by a deposit of limestone rising like 

 them to the S.E. but at an angle not exceeding 5°. The outburst 

 of the limestone may be traced in a direction N.E. and S.W 



