382 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
other stratified rocks occur, representing the strata through which the vents 
were diilled. In the tufis ot tlie Itaglesliam district pieces of grey and pink 
granite have been met with which, if they are portions of an old granite 
mass below, must have come from a great depthd In the coarser tuffs 
and agglomerates a larger variety of lava-form rocks is to be found than 
can be seen among the bedded lavas of the Plateaux. They include felsites 
and quartz-porphyries, and more rarely basic lavas (diabases, etc.). 
^ Explanation of Sheet 22 Ocol. Siirr, Scot p. 12. 
