ANNIVEKSAET ADDRESS OF THE PRESIDENT. I49 



lie the intercalated volcanic rocks, cover several detached areas in 

 Ayrshire and Dumfriesshire. Lithologically these strata present a 

 close resemblance to the Penrith sandstone and breccias of Cumber- 

 land, the Permian age of which is generally admitted. They lie 

 unconformably sometimes on Lower and Upper Silurian rocks, 

 sometimes on the lower parts of the Carboniferous system, and 

 sometimes on the red sandstones which form its highest subdivision. 

 They are thus not only younger than the latest Carboniferous 

 strata, but are separated from them by the interval represented by 

 the unconformability. There can thus be little hesitation in re- 

 garding them as not older than the Permian period. 



The only palgc-ontological evidence yet obtained from these rocks 

 in Scotland is that furnished by the well-known footprints on the 

 red sandstone of Annandale. These impressions indicate the exist- 

 ence of early forms of amphibians or reptiles during the time of 

 the deposition of the red sand. The precise zoological grade of 

 these animals has never yet been determined, so that they furnish 

 little help towards fixing the stratigraphical position of the red 

 rocks in which the footprints occur. 



II. Structure. — That the volcanic rocks now to be described belong 

 to the time of the red sandstones with which they are associated is 

 abundantly clear. They consist of lavas and tuffs, which are in some 

 places underlain and everywhere overlain with these sandstones, 

 which contain likewise interstratifications of them. Unfortunately, 

 however, so enormous has been the denudation of the country that 

 these rocks have been worn away from wide tracts which they almost 

 certainly once overspread. The result has been that while the 

 lavas and tuffs ejected at the surface during Permian time have 

 been reduced to merely a few detached fragments, the progress 

 of denudation, by removing this superficial volcanic casing, has 

 revealed the vents of discharge to an extent unequalled in any 

 older geological system, even among the puys of the Carboniferous 

 period. The Permian rocks, escaping the effects of those great earth- 

 movements which dislocated, plicated, and buried the older Palaeozoic 

 systems of deposits, still remain for the most part approximately 

 horizontal or only gently inclined. They have thus been more 



Binney, ibid. vol. xii. (1856) p. 138, vol, xviii. (1862) p. 437; Harkuess, ibid. 

 vol. xii. (1856) p. 262. The rocks are mapped more especially in Sheets 9, 14, 

 and 15 of the Geological Survey of Scotland, to which, and their accompanying 

 explanations, reference is made. 



VOL. XLVIII. I 



