CARBONIFEROUS VOLCANIC ROCKS OF THE FIRTH OF FORTH BASIN. 453 
vents spread over a considerable area. The subjoined section (fig 1), may serve 
as an illustration of the relation between this sheet of bedded tuff and the 
underlying rocks. 
Fig. 1.—Section in brooks between Bonnytown and Baldastard, Largo. 
a, Sandstone shales and coals of Carboniferous limestone series ; 6, Unconformable tuff. 
No proof could be more satisfactory that volcanic action was abundant in 
the east of Fife long after the formation of the latest member of the Scottish 
Carboniferous system. It is not impossible that some of the detached vents in 
other parts of the basin of the Firth of Forth may belong to as late a period. 
I have already suggested that this is probably the date of the later part of 
Arthur Seat. Some years ago I described a somewhat similar series of vents 
which pierce the Coal-measures of Ayrshire, and are connected with truly inter- 
bedded volcanic sheets in the overlying Permian sandstone series.* The Fife 
volcanoes may with much probability be referred to the same period. 
Were there no other evidence to fix the epoch of volcanic activity in the 
east of Fife, it would be most logical to exclude the volcanic rocks of that 
district from the list of those belonging to the Carboniferous period. But to 
the north of Largo, and still more distinctly to the north-east of Leven, sections 
occur to show the contemporaneous outpouring of volcanic rocks in the 
Carboniferous Limestone period. The Leven section, seen in a ravine a little 
to the north-east of the town, is specially important. It presents a succession 
of red and green fine sandy tuffs, interstratified with fire-clays and sandstones, 
and containing a zone of basalt in the centre. These rocks lie not far from the 
top of the Carboniferous Limestone series. They prove that at least in one part 
of the district, volcanic action manifested itself long before the latest Carboni- 
ferous or Permian outbreak. It is quite pussible, therefore, that some of these 
vents, the relations of which to the surrounding rocks are not such as to prove 
them to be of the latest date, may belong to some part of the time occupied 
by the deposition of the Carboniferous Limestone. I have not been able to 
discover any satisfactory means of discriminating them. I believe that if such 
older vents exist at all, they can form but a small minority among those which, 
on the grounds already stated, may be assigned to a much later period. But I 
have glady availed myself of this uncertainty, to include in this memoir an 
account of the east of Fife volcanic rocks, as they illustrate the phenomena of 
vents more fully than those of any other district in Scotland. 
* “ Geological Magazine,” vol. iii, p. 243. 
VOL, XXIX. PART I. OA 
