648 MR ARCHIBALD GEIKIE ON THE CHRONOLOGY 
pursued, will be known when the geology of Stirlingshire and the area to the | 
south-west comes to be thoroughly worked out, but my examinations have : 
carried me no further at present. The trap-rocks of Linlithgowshire are, so far | 
as I yet know, the latest Carboniferous traps in Scotland. : 
Fig. 1—Diagram-section to show the intercalation of sheets of volcanic material among the 
Carboniferous strata of the Bathgate Hills. 
Bathgate. Borrowstounness 

_ 
oo ceca 
c. Carboniferous Sandstones, Shales, Coal, and Ironstones. 1, Carboniferous Limestone. 
g- Sheets of Greenstone and Basalt. a. Beds of Stratified Ash. 
In quitting the Carboniferous system, let me repeat in one sentence that this 
group of rocks, as displayed in the region of the Lothians, shows a regular suc- 
cession of contemporaneous igneous rocks throughout its entire thickness; that 
- the volcanic forces first broke out about the centre of the district at Edinburgh ; 
that, after becoming quiescent there, they reappeared simultaneously at the time 
of the Burdiehouse limestone in East and West Lothian; that by the time of the 
Carboniferous Limestone they had become extinct in the former area, but gradu- 
ally increased in energy in the latter, where they continued in operation at inter- 
vals throughout the rest of the Carboniferous period. 
At this point there lies a wide gap in the evidence. Of Permian or Triassic 
trap-rocks I am not aware that Scotland has yet furnished any examples; and 
thus, leaving the greenstones of the Carboniferous, we pass to those of the 
Oolitic group. 
Traps of Oolitic Age. 
That wild, rocky chain of islands known as the Inner Hebrides, extending 
from Oban to the Shiant Isles, consists mainly of vast trappean masses, overlying 
and interstratified with limestones, shales, and sandstones, which in their fossils 
correspond to the English Lias and Oolite as far upwards as the Oxford Clay. 
The Lias of Skye is much traversed by dykes of greenstone and basalt, and 
likewise cut through and metamorphosed by great hills of syenite. It presents, 
however, no trace of contemporaneous ejections, though, as I have elsewhere 
shown,* some of its beds, by their brecciated and unconformable character, afford 
indications of such subterranean movements as, in the succeeding Oolitic period, 
produced the greater part of the mountains of Skye and Raasay. The dykes and 
likewise the syenites are of two ages, the whole being probably later than the 
* Quart. Jour. Geol. Soc., vol. xiv. 

