CARBONIFEROUS VOLCANIC ROCKS OF THE FIRTH OF FORTH BASIN. 457 
shire, expose many ground-plans of the vents, and permit these irregularities 
to be closely examined. The accompanying figure (fig. 3), exhibits some charac- 
Fig, 3.—Ground plan of volcanic vents. 
teristic forms of vents. Some of the eccentricities of outline no doubt arose 
from the irregular way in % 
which the rocks through 
which an orifice was drilled 
yielded: to the forces of 
explosion. This is often 
well shown by the veins 
and nests of tuff or ag- 
glomerate which have been 
forced into the rents or 
sinuosities of the orifices. 
In other cases, however, 
it is probable that what e 
appears now as. one SO 
voleanic neck, was the i 
S 
Fig 4.—Plan of volcanic necks at Kellie Law, east of Fife. 1, Kellie Law 
result of a shifting of the (tuff) ; 2, Carnbee Law (tuff); 3, 4, 5, small tuff necks; BB, basalt 
actual funnel of discharge, 
dykes and sheets; cc, coal-seams; 7, limestone; /, fault. The arrows 
mark the dip of the strata through which the necks have been drilled. 
so that the neck really represents several closely adjacent vents. The 
necks at Kellie Law (fig. 4) show this arrangement very 
clearly. The Law itself (1) probably consists of two 
contiguous vents, while a third (2) forms a smaller cone 
immediately to the east. This slight lateral displace- 
ment of the vent has been noticed at many Tertiary 
and recent volcanic orifices. In the island or peninsula 
of Volcanello, for example, I observed three craters 
indicative of successive shiftings of the vent, the most 
perfect crater marking the latest and diminishing phase 
Fig. 5.—Plan of the craters in 
Voleanello, Lipari Islands. 
of the volcanic activity. The cones at Kellie Law may point to a similar 
series of events: 
VOL, XXIX. PART I. 
6B 
