474 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
in tlie Carboniferous Limestone sez’ies. Thns the great sill between Stirling 
and Kilsyth keeps among the lower parts of that series. On the same 
general horizon are the vast sheets of dolerite which stretch through Fife in 
the chain of the Cult, CleLsh, and Lomond Hills on the one side, and in the 
eminences from Torryburn to Kinghorn on the other, though the intrusive 
material sometimes descends almost to the Old Eed Sandstone. In Linlith- 
gowshire and Edinburghshire, as well as in the south of Fife, the sills 
traverse the Caleiferous Sandstone groups. 
If the horizons of the sills furnished any reliable clue to their age, it 
might be inferred that the rocks were all intruded during the Carboniferous 
period, and as most of them lie beneath the upper stratigraphical limit of 
the puy-eruptions, the further deduction might be drawn that they are 
connected witli these eruptions. I have little doubt that in a general sense 
both conclusions are well-founded. But that there are exceptions to the 
generalization must be frankly conceded. On close examination it will be 
observed that the same intrusive mass sometimes extends from the lower 
into the upper parts of the Carboniferous groups. Thus, in the west of 
Linlithgowshire, a large protrusion which lies upon the Upper Limestones, 
crosses most of the Millstone Grit, and reaches up almost as high as the 
Coal-measures. Again, in Fife, to the east of Loch Leven, a spur of the 
great Lomond sill, crossing the C'arlioniferous limestone, advances southward 
into the coal-field of Ivinglassie. In Stirlingshiie and Lanarkshire numer- 
ous large dolerite sheets have invaded the Millstone Grit and Coal-measures, 
mcluding even the upper red sandstones, which form the top of the Carbon- 
iferous system in this region. It is thus olivious that if the puy-eruptions 
in the basin of the Forth ceased towards the close of the deposition of the 
Carboniferous Limestone series, there must have been a subsequent injection 
of basic lava on a gigantic scale in central Scotland. I shall recur to this 
subject in Chapter xxxi. 
2. NORTH OF AYR, SHIRE 
^ In this part of the country another group of puys and their associated 
tuffs and lavas may lie traced from near Dairy on the west, to near Galston 
EiarJUket Castle 
Fig. 173. Section aemss the Upiier Volcanic Band of north .Ayrshire. Length about four miles. 
2. Tuffs Closins the Plateau volcanic serie.s ; 3. Hurlet Liine.stone ■ 
^hper volcanic band; ff. 
on the east (Map H .). The length of the tract is aliout sixteen miles, wdiile 
its breadth varies from about a furlong to nearly a mile and a half. I have 
had occasion to allude tti this marked baud of volcanic materials which here 
