BOOK YII 
THE TERM IAX VOLCANOES 
CHAPTER XXXI 
THE PERMIAN "VOLCANOES OF SCOTLAND 
Geographical Changes at the Close of the Carboniferous Period— Land- and Inland-Seas 
of Permian time— General Characteristics and Nature of the Materials erupted— 
Structure of the several Volcanic Districts: 1. Ayrshire, Nithsdale, Annandale ; 2. 
Basin of the Firth of Forth. 
The close of the Carboniferous portion of the geological record in Britain is 
marked, by another of those great gaps which so seriously affect the con- 
tinuity of geological history. No transitional formation, such as in othei 
countries marks the gradation from the Carboniferous into the succeeding 
period, has been definitely recognized in this country. The highest Carbon- 
iferous strata are here separated from all- younger deposits by an uncon- 
formability, indicating the lapse of vast periods of time whereof, within the 
British area, no chronicle has been preserved. 
When we pass from the Carboniferous system to that which comes next 
to it in order of time, we soon become sensible that great changes m 
geography, betokening an immense interval, took place between them. The 
prolonged subsidence during which the Coal-measures were accumulated, not 
only carried down below sea-level all the tracts over which the Carbon- 
iferous system was deposited, but possibly submerged the last of the islets, 
which, like those of Charnwood Forest, had survived so many geological 
changes. Eventually, however, and after what may have been a vast 
period of quiescence, underground movements began anew, and the tracts of 
Coal-measures were unequally ridged up into land. The topography thus 
produced appears to have resulted in the formation of a series of inland 
seas somewhat like those of the Old Red Sandstone, but probably less m 
area and in depth. In these basins the water seems to have been on the 
whole unfavourable to life, for the red sand and mud deposited in them are 
