to . 
CHAP. XXXI 
THE BASIN OF THE FIRTH OF FORTH 
69 
That a new vent should be opened, after the lapse of one or more 
eological periods, on or near the site of more ancient volcanic orifices W an 
incident of which, as we have seen, the geological history of th ® J )1 J ls 
Isles furnishes a number of examples. It will be remembered that little 
more than a mile to the south of Arthur Seat lies the great vent of the 
Braid Hills, which in the time of the Lower Old Bed Sandstone gave 01 
such a huge pile of lavas and tuffs. Volcanic energy thereafter entirely 
died away, and in this district was succeeded by a prolonged period of 
quiescence, during which the Lower Old Bed Sandstone was upraised and 
extensively denuded, while the Upper Old Bed Sandstone was deported. At 
length, in the immediate neighbourhood, from one or more vents, the exact 
site of which is not certainly known, the older lavas and tuffs of Ait 
Seat Calton Hill and Craiglockhart Hill were erupted. Again, after another 
vast interval, a new volcano appeared, and the agglomerate and younger 
basalts of Arthur Seat were ejected from it. This is one of the most 
striking examples in this country of the remarkable persistence of volcanic 
energy in the same locality. ... . f 
There is no evidence at Arthur Seat itself to fix the geological date 0 
the last volcanic activity of the hill. If the group of : younger 
alone, with no other trace of post-Carbomferous eruptions m the sunom 1 
ing district, a plausible conjecture as to its age would not be earfy _ offered. 
But in reality it is not a solitary example of such rocks ; for with 11 sight, 
on the opposite side of the Birth of Bortli, its counterparts may be seen. 
To tim Ts'rUn of these numerous and clearer illustrations 1 now 
The East of Bife is remarkable for a large assemblage ot v ulcanic v ents, 
which, unlike those in Ayrshire and Nitlisdale, stand alone, their superficial 
ejections having been removed by denudation, and no connection being traceable 
Seen them end a„y Persian sandstones. The vents filled up vntfi agglotne- 
rate and pierced with plugs and veins of basalt, rise through the Carboniferous 
rocks, but have left no record for precisely defining their geological age. On 
the one hand, it is quite certain that in this district volcanic eruptions took 
place during the earlier half of the Carboniferous period. To the north ot 
Largo, and still more distinctly to the north-east of Leven, sections occur 0 
show the contemporaneous outpouring of volcanic rocks during the time of 
the Carboniferous Limestone. The Leven section, seen 111 a ravine a little 
to the north-east of the town, is specially important. It presents a succes- 
sion of red and green fine sandy tuffs, hit ^stratified with fire-clays and 
sandstones, and containing a zone of basalt 111 the centie. mse ioc^ 
not far from the top of the Carboniferous Limestone series 
On the other hand, there is equally clear proof of far later eruptions. 
Brom St. Andrews to Elie a chain of necks may be traced, having the same 
general characters, and piercing alike the Calciferous Sandstones and 
the older part of the Carboniferous Limestone series. That these 
vents must in many cases be long posterior to the rocks among * J ‘ j 
rise, is indicated by some curious and interesting kinds of evide ■ 
