1845. J 605 



In the lowei' undulating country to the south of that hill, 

 the same strata (including the Pentamerus limestone) are cut 

 through by many courses of eruptive rock, some of which (as at 

 Velo) consist of a reddish rhombic porphyry, having a base of 

 granite and compact felspar, and others of hornblendic greenstone, 

 flanked by highly allied subcrystalline ferriferous red strata, 

 which, at a little distance from the intruding masses, assume the 

 aspect of the ordinary red rah of Pembrokeshire. The chief of 

 these bands and dykes of eruptive matter (some of which having a 

 felspathic base, are changed into crystals of felspar and lime) 

 usually traverse the Silurian beds from N. N. E. to S. S. W. 



Following these porphyritic and greenstone rocks to Klekken, 

 they are seen in some places to cut through, and in others to throw 

 up into domes the Silurian strata. Struck with the apparent 

 multitude of these little undulations, and desirous of ascertaining 

 what was the real geological equivalent of the band marked " harte 

 schiefer" on the map of Keilhau, my friend Professor Forch- 

 hammer and myself made a traverse from the village of Klekken on 

 the west to the mountain chalets of Hong on the east, where 

 large masses of granitic and porphyritic rocks rise to the same 

 table land as that of which the section (p. 469.) exposes a part. 

 In the lower undulations we observed a number of greenstone 

 dykes trending from E. by N. to "W. by S., every little ridge 

 being characterized by a nucleus of such rock, and its flanks 

 composed of jet-black anthracitic schist, and some impure lime- 

 stone. Parallel to these dykes and nearer to the mountain side, is 

 a strong band of rhombic porphyry, whilst other dykes (apparently 

 traversing those of which I have been speaking) constitute a net- 

 work of intrusive matter. 



Owing to the short time at our disposal, we could not then de- 

 termine whether the rhombic porphyry or the greenstone were the 

 last ejected, but our observations in the country of Ringerigge, 

 where greenstone cuts through the porphyritic plateau, led us to 

 conclude that as the porphyry was unquestionably formed pos- 

 teriorly to the old red sandstone, so the greenstone was the most 

 recent of these eruptive masses. As we ascended the mountain 

 side, the calcareous shale and limestone which forms a mural and 

 slightly altered mass in the valley with a strike conforming to 

 the direction of the chief eruptive bosses (E. by N. to W. by S.), 

 becomes more and more indurated, and in one place, where the 

 beds resumed their prevalent strike of N. by E., and S. by W., 

 they are cut through by transverse east and west dykes of greenstone. 

 On approaching the summit called the Rong Stein or the summer 

 pastures of the village of Hong, the sedimentary mass may there be 

 considered as a great flap of the granitic and porphyritic mountain, 

 and is then in a still more altered state, assuming what geologists 

 used formerly to call a very ancient aspect. The schist becomes 

 brittle, crystallised, and compact, and is the "Harte Schiefer " 

 of Keilhau; whilst the calcareous nodules have disappeared, leaving 

 cavities in the schist, which still distinctly mark the original lines 



