208 ON THE ORIGIN, MATERIALS, COMPOSITION, 



in the manner which they do. That limestone is 

 actucilly thus consolidated after fusion, even in large 

 masses, is also proved, as far as any thing relating to 

 the influence of trap is proved, by the conversion of 

 conchiferous secondary strata, in those situations, into 

 crystalline limestone ; a fact occurring very extensively 

 and demonstrably in Sky, and recorded in my work on 



the Western Islands. 







With respect to Serpentine, the whole question is 

 as yet involved in darkness. It is not known that it 

 can he formed from water, and I have proved, that as 

 it passes into trap, it can he formed by fusion. 



All the scaly schists, of which micaceous schist 

 may here represent the whole, present characters 

 which are scarcely explicable without admitting the 

 action of both these agents. The stratified disposition 

 and the laminar form, give indications of a deposition 

 from water; and if any doubt of that could remain, 

 it is removed by finding that, in many places, it con- 

 tains fragments of discordant rocks, of granite, for 

 example, limestone, and quartz rock. It has further 

 been held, that the parallel position of the mica is in 

 itself a sufficient proof of deposition, because, it is 

 the necessary position, and because the same circum- 

 stance exists in the micaceous sandstones, so analogous 

 to it, which are actually deposited from water. But 

 this, if probable, is an equivocal circumstance; as I 

 have observed that, in hypersthene rock, a member 

 of the trap family, and even in some rare trap veins 

 that contain mica, in the Western islands, as well as 

 in veins of antient porphyry, the flat crystals of hy- 

 persthene in one case, and the mica or pinite in the 

 others, preserve that parallelism which must here be 

 attributed to the polarity of crystallization operating 



