150 



THE GEOLOGIST. 



North of Marlborough, where it is thick, the chalk-rock appears to have given 

 rise to two escarpments (an upper and lower one), in the chalk range. 



Fossils are usually rare in this bed; but Mr. J. Evans, E.G.S., collected 

 several from it near Boxmoor ; and amongst them is the genus Belosepia 

 (hitherto known only as tertiary) ; -Baculitus, Nautilus, Turrilites, Solarium, 

 Inoceramtis, Parasmilia, and Ventriculites are here represented ; and the follow- 

 ing species have been identified — Litorina monilifera and a new species, Pleuro- 

 tomaria, sp. Myacites mandibula, Spondylus latus, Sp. spinosus, Rhynchonella 

 Mantelliana, Texebratulata biplicata, and T. semiglobosa. 



The fossils mostly have a lower-chalk character. Two species, Littorina 

 monilifera, and Myacites mandibula, have not been noticed in England above the 

 Upper Greensand. 



February 6, 1861. 



" On the Altered Rocks of the Western and Central Highlands." By Sir 

 R. I. Murchison, E.R.S., Y.P.G.S., and A. Geikie, Esq, E.G.S. 



In the introduction it was shown that the object or this paper was to prove 

 that the classification which had been previously established by one of the 

 authors in the county of Sutherland was applicable, as he had inferred, to the 

 whole of the Scottish Highlands. The structure of the country from the 

 borders of Sutherland down to the western part of Ross-shire was detailed, and 

 illustrated by a large map of Scotland coloured according to the new classication, 

 and by numerous sections. Everywhere throughout this tract it could be 

 proved that an older gneiss, which the authors called " Laurentian," was over- 

 laid unconformably by red Cambrian sandstones ; these again uneonformaVy 

 by quartz-rocks, limestones, and a gneissose and schistose series of strata, as 

 previously shown in the typical district of Assynt. Erom the base of these 

 quartz-rocks a perfect conformable sequence was shown to exist upwards into 

 the gneissose rocks, which is not obliterated by granite or any similar rock. 



The tract between the Atlantic and the Great Glen consists, according to the 

 authors, of a series of convoluted folds of the upper gneissose rocks, until, 

 along the line of the Great Glen, the underlying quartzose series is brought 

 up on an anticlinal axis. A prolongation of this axis probably exists along 

 part of the west coast of Islay and Jura, two islands which exhibit a grand 

 development of the lower or quartzose portion of the altered Silurian rocks of 

 the Highlands. 



Erom the line of the Great Glen north-eastward to the Highland border, the 

 country was explained as consisting of a great series of anticlinal and synclinal 

 curves, whereby the same series of altered rocks which occur on the north- 

 west is repeated upon itself. One synclinal runs in a north-east and south-west 

 direction across Loch Leven. The anticlinal of quartzose rocks that rises 

 from under it to the south-east spreads over the Bredalbane Eorest to the Glen 

 Lyon Mountains, where it sinks below the upper gneissose strata with their 

 associated limestones. Ben Lawers occupies the synclinal formed by these 

 upper strata, and the limestones and quartz -rock come up again in another 

 anticlinal axis corresponding with the direction of Loch lay. The continuity 

 of these lines of axis was traced both to the north-east and south-west. 



It thus appeared that the crystalline rocks of the Highlands are capable of 

 reduction to order ; that the same folds and curves could be traced in them as 

 in their Less altered equivalents of the South of Scotland; and that in what 

 had hitherto appeared as little less than a hopeless chaos, there reigned a regu- 

 lar ami beautiful simplicity. 



1 n conclusion, Sir Roderick Murchison vindicated the accuracyof his published 

 seel ions in i hr noil h-west of Sutherland, which had been approved after personal 

 inspect ion by Professors Ramsay and Harkness ; and he gave detailed reasons 

 for disbelieving the accuracy of the sections recently put forth by Prof. Nichol, 



