1 2 Proceedings of the Boyal Physical Society. 



of the traps of Faroe, and which to me were instructive, 

 as an indication of the method by which these immense 

 trappean beds were deposited. It has been admitted by 

 most mineralogists that calcedony is formed by the aqueous 

 method, and not subjected to any violent heat ; so here we 

 have a proof, that the matrix or trap was not exposed to 

 igneous fusion, and that the calcedonies and zeolites were 

 metamorphic after the deposition of the trap. That these 

 immense beds were of volcanic origin, no one will be bold 

 enough to deny ; that they were subaqueous I cannot doubt, 

 by the evidence they bear of having been horizontally 

 arranged by water, and that, while at a comparatively high 

 temperature, they were subjected to the action of gases 

 under great tension, causing the vesicular cavities which are 

 now filled with calcedonies and zeolites, — the evidence of long 

 continued metamorphism. That these islands have risen at 

 a period when the upper layers were still, if not plastic, yet 

 containing much volatile matter, is evident from the columnar 

 effects seen on all their summits, caused, certainly, not by 

 igneous crystallisation but merely shrinkage. These pillars 

 are always, as has been often pointed out to us by our late dis- 

 tinguished President, Professor Fleming, at right angles to 

 the strata beneath. 



The first glimpse of Iceland, to one who has from boyhood 

 made it his hope and day-dream to visit it, was certainly very 

 grand and impressive, as our eyes rested on the magnificent 

 Oraefa Yokul, the highest mountain in the island. But as 

 our aim was more scientific than scenic, we were more in- 

 terested, as we approached the great chasm or crater of Kot- 

 lugja, which so lately as 1860 devastated the whole country 

 around with a deluge of mud and showers of ashes. This 

 enormous rent, which we reckoned equal to the whole length 

 of Glen Eosa in Arran, is evidently so steep, that the snow 

 does not lie on its sides, and there it stands in gloomy 

 grandeur, on the haunch of an immense ice mountain, the 

 Myrdals Yokul. Skirting the shore, we were much gratified 

 by the sight of one of the largest glaciers in the plain, and, 

 as we commanded the whole position, had a finer opportu- 

 nity than we ever enjoyed in Switzerland, of observing the 



