148 PROCEEDIXGS OF THE GEOLOGICAL SOCIETY. 



but it was only a part, and possibly only a small part, of the total 

 interval between the cessation of eruptive activity in Carboniferous 

 and its re-commencement in Permian time. A considerable frag- 

 ment of the geological record is obviously missing in Britain after 

 the end of the Carboniferous formations. We have none of those 

 Permo-Carboniferous strata which elsewhere connect the Coal 

 Measures with the Permian rocks. Whether, had this gap been 

 filled up here, it would have supplied any trace of contemporaneous 

 volcanic action cannot be determined. All that we know is that, 

 in the Permian period, after the long interval just referred to, 

 volcanic activity in a greatly enfeebled manifestation once more 

 broke out. 



I, DisTEiBUTioisr. — The rocks now to be described exhibit a still 

 more restricted range than those of the Carboniferous period. They 

 are developed, indeed, only in two widely separated regions. Of these, 

 the largest and most important lies in the centre and south-west of 

 Scotland, forming either two distinct tracts or extending in a 

 straggling band from the east of Fife across the basin of the Pirth 

 of Porth to the north of Ayrshire, and thence, with a more per- 

 sistent and well-developed series of volcanic records, through the 

 centre of that county into Mthsdale and several of the adjacent 

 valleys, even as far as Annandale. There the volcanic rocks end, 

 although the red sandstones continue into Cumberland, and are 

 largely exhibited in the Midland and South-western counties of 

 England. Not until we reach the neighbourhood of Exeter do we 

 again encounter volcanic rocks associated with any portion of the 

 ' poikilitic' rocks of England. There is thus a northern or Scottish 

 and a southern or Devonshire region in which volcanic records are 

 preserved which we have now to consider. 



Twenty-five years ago I was able to announce the existence of 

 traces of a group of Permian volcanoes in the south-west of Scot- 

 land.^ Various additions to our knowledge of them have been 

 made during the interval, but the main facts remain much as they 

 were then stated by me. No fossils have yet been obtained to fix 

 with more precision the age of the rocks among which these vol- 

 canic records are preserved. But the extension of the detailed 

 mapping of the Geological Survey has confirmed the original infe- 

 rence as to the stratigraphy.^ The red sandstones, among which 



1 Geol. Mag. for 1866, p. 243,and Murchison's * Siluria,' 4th ed. (1867) p. 332. 



2 On the age of these sandstones, see Murchison's * Siluria,' 4th ed. p. 331 ; 

 Quart. Journ. Geol. Soc. vol. vii. (1851) p. 163, note; vol. xii. (1856) p. 267; 



