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Observations on the mountain Ben Nevis, and on some other places 

 in Scotland. 



The authors of this communication, two Prussian naturalists, have 

 here presented their observations on someot the more interesting por- 

 tions of Scotland, which they visited about three years ago, with a view 

 to a comparison of the rocks of Great Britain with those of the continent. 



1. The Paper commences with a description of the great barrier of 

 the Caledonian Canal : High mountains of crystalline rocks form its 

 western boundary} conglomerate and sandstone, with subordinate beds 

 of black calcareous shale, reach from the east to the upper end of 

 Lochness ; on the banks of the river of that name, is a flat pebble 

 beach 150 feet higher than the sea, portions of which form islands that 

 have the aspect of old fortifications. 



Ben-Nevis is wholly crystalline : its summit consists of felspar- 

 porphyry ; its sides of granite, which rises to the height of 3000 feet 

 above the sea, and is bordered by gneiss and mica-slate. 



Near Invertochy Castle, a low rock projecting above the surface 

 of the bog, consists of mica-slate, alternating, as in the valley of the 

 Spean, with gray granular limestone. 



On the N. of Ben-Nevis, sienite containing mica and hornblende, 

 both of them black, and therefore easily confounded, forms below the 

 granitic declivity a narrow ridge nearly 1000 feet high. 



On the right bank of Glen-Nevis, the schistose rocks are lower 

 towards the west, and repose on the steep side of the granite, small 

 hollows, however, intervening} they soon disappear on the north, 

 but gain ground eastward. 



A single summit only, of Glen-Nevis, consists of mica-slate ; beneath 

 are chlorite slate, and a rock composed of alternate lamina? of com- 

 pact white felspar and green mica ; in the hollow below is contorted 

 gneiss, connected intimately with the rock just described, or rather 

 passing into it. 



Compact white, and pale-green felspar occurs frequently in the 

 slates, at and near their junction with the granite. 



The granite at the sides of Ben-Nevis is large-grained, composed 

 of flesh-coloured felspar, albite, gray-quartz, and black mica in equal 

 proportions ; higher up, it loses the albite and quartz, acquires a few 

 specks of hornblende, and passes into a kind of felspar-porphyry j 

 which last-mentioned substance constitutes the summit. 



The junction of the granite and porphyry is laid bare on the E. and 

 S. sides of the mountain 5 but on the N. and W. is concealed by 

 scattered blocks of porphyry. 



At the head of Glen Ptarmigan, is a steep cliffof porphyry, at least 

 1500 feet high. Its shape is that of an oblique four-sided pyramid, 

 irregular and truncated, rising on the east and south, through the 

 granite ; and not merely overlying it, as M. Boue supposed. This 

 fact the authors consider themselves as having fully established. 



With equal confidence they affirm, that the gneiss and mica-slate 

 are not conformable to the granite ; and that the latter has forced its 

 way through them : the granite traverses them also in the form of veins. 



They remark further, the frequent occurrence of compact felspar, 

 where these substances adjoin the granite. 



