CHAP. XXVIII 
PUYS OF THE FIRTH OF FORTH 
473 
aiul apart from the geological horizons on which they lie, they form a wide 
ring surrounding the Falkirk and Stirlingsliire coal-field. 
Beginning at the Aljbey Craig, near Stirling, we may trace this ring as 
a_ continuous belt of high ground from Stirling to the Eiver Carron. Thence 
it splits up into minor masses in different portions of the Carboniferous 
system, and doubtless belonging to different periods of volcanic disturbance, 
but yet sweeping as a whole across the north-eastern part of the Clyde 
coal-field, and then circling round into Stirlingshire and Linlithgowshire. 
There are no visible masses to fill up tbe portion of the ring back to Abbey 
Craig. But through Linlithgowshire and the west of Edinburghshire a 
number of intrusive sheets form an eastward prolongation of the ring. 
Large as some of these sheets are at tlie surface, for they sometimes exceed two 
or three square miles in area, a much larger portion of their mass is generally 
concealed below ground. Mining operations, for example, have proved that 
in the south-east of Linlithgowshire areas of intrusive rock whieli appear as 
detached bosses or bands at the surface are connected underneatli as por- 
tions of one continuous silt, which must be several square miles in extent. 
But it is in Fife that the sills reach their greatest develojnnent among 
the Carboniferous rocks of Scotland (Fig. 172). A nearly continuous Ijelt of 
them runs from the Cult Hill near Saline on the west, to near St. Andrews 
West Lomond ( 17131 !) 
Fifi. 172.— Section acro.ss the Fife band of Sills. 
1. Upper Old Red Sandstone ; 2._ Calciferous Sandstones ; .B. Carboniferons Limestone series ; J. Jlillstone Grit • 
0 . Coal-Bieasiires ; 6. Dolerite Sills. /, Fault. ’ 
on the east, a distance of about 35 miles. This remarkable liand 
is connected with a less extensive one, wltich extends from Torryburn on 
the west, to near Kirkcaldy on the east. In two districts of the Fife region 
of silks, a connection seems to be traceable between the intrusive sheets and 
volcanic vents, at least groups of necks are found in the midst of the sills. 
One of these districts is that of the Saline Hills already described, the other 
is that of Burntisland. In the latter case the evidence is especially striking, 
for the vents are connected above with bedded lavas and tuffs, wiiile lielow 
lie three well-marked sills (Fig. 159). 
It is certainly worthy of remark that sills are generally absent from 
those areas where no traces of contemporaneous volcanic actiMty are to be 
found. No contrast in this respect can be stronger than that between the 
ground to the east and west of the old axis of the Bentland Hills. In the 
western district, where the puys are so well displayed, sills abound, but in 
the eastern tract both disappear. 
Another question of importance in dealing with the history of these sills 
is their stratigraphical position. By far the larger proportion of them lies 
