Geikie — Permian Yolcanos in Scotland. 243 



glacier-action, atmospheric erosion, or marine denudation, to that of 

 the mysterious but vast and indubitable subterranean forces, daily- 

 exemplified in the volcano and the earthquake, as by no means the 

 least energetic or efficient among the agencies that have been always 

 operative in modelling the superficial features of our globe. I ven- 

 ture to think that this branch of geology has been of late under- 

 valued, not to say neglected. 



11. — Traces of a G-koup of Permian Voloanos in the South- 

 West OF Scotland. 



By Archibald Geikie, F.R.S., etc. 



ALTHOUGtH volcanic rocks of Permian age have long been known 

 to occur abmidantly in Germany, their existence in Britain does 

 not appear to have been recognized up to the present time. Trap- 

 dykes, indeed, are far from rare among our Permian strata; there 

 occur likewise many igneous masses penetrating the higher portions 

 of the Carboniferous formation ; but the foi-mer are evidently later 

 than the Permian period, while the latter may be anterior to it. The 

 history of volcanic action in the British isles, so far as I am aware, 

 embraces as yet no clear evidence of Permian volcanos. In the pre- 

 sent commimication I propose to fill up this gap by showing that 

 during the formation of the Permian sandstones a series of small but 

 active volcanos was scattered over the south-west of Scotland. 



After the labours of Sir E. I. Murchison, Mr. Binney, and Professor 

 Harkness,^ it is now admitted that the red sandstones which range 

 from Cumberland into Dumfriesshire, and ascending Nithsdale, 

 stretch in inteiTupted patches or basins as far as the Yalley of the 

 Ayr, are of Permian age. In Ayrshire they occupy a well defined 

 area about six miles long by four or five broad, traversed by 

 the river Ayr, which has worn through them a succession of pic- 

 turesque ravines. The basin which they thus form rests upon the 

 upper red portion of the Carboniferous grouj). At the eastern edge 

 of the basin to the south of the village of Mauchline the Ayr has 

 laid open a section which has been described by Mr. Binney and 

 Mr. Harkness. The bottom of the brick-red Permian sandstone is 

 there seen to rest conformably upon and pass down into a rock 

 called by both these observers a " breccia," and classed by them 

 with the Permian breccias of Dumfries and the north-west of 

 England. A more extended examination of the district has enabled 

 me to connect this " breccia " with other similar deposits, and with 

 wide sheets of felspathic trap, as parts of a series of volcanic rocks 

 interstratified with the base of the Permian sandstones of Ayrshire. 



1 Murchison, Siluria,-p. 351, Quart. Journ. Geol. Soc. vii. 163; xii. 267. Binney, 

 Id., vol. xii. (1856) p. 138. Harkness, Id., p. 262. It was not the object 

 of these observers to investigate the igneous rocks of the Ap-, and they treated 

 them simply as intrusive masses, though the singular aspect of the "breccia" 

 led Mr. Binney to remark that "the cementing paste has much the appear- 

 ance of felspathic ash." In a later paper (Quart. Journ. Geol. Soc, vol. xviii. 



