360 
Proceedings of the Royal Society 
ral relation of the rocks between the Carboniferons and Upper 
Silurian formations in the middle of Scotland is shown. 
Fig. 2. — Sketch-section across the Cairn Hills, Pentlands. 
EAST CAIRN HILL 
a, Upper Silurian shales ; &, Red sandstones and eonglomerates, supposed to be the base of the 
Lower Old Red Sandstone ; c, Thick conglomerates and grits, forming a Middle division of 
the Old Red Sandstone ; d, Felstone lava-beds, interbedded with c ; e, Upper Old Red Sand- 
stone ; /. Carboniferous sandstones, shales, &c. ; g. Intrusive greenstone coming up along a 
line of fault; h, Fault. 
The Upper Old Ked Sandstone has been mapped by the Survey 
throughout the Lothians and Fife, and has been traced southwards 
far into Berwickshire, and south-w^estwards into the uplands of 
Lanark. Traces of contemporaneous volcanoes at the top of the 
Old Ked Sandstone have been found near Dunse, in Berwickshire,* 
and near Uunsyre in Lanarkshire. 
The mapping out of the various subdivisions of the Carboniferous 
rocks has opened up some curious questions regarding the ancient 
physical geography of the country, and unequal oscillations of level 
during the Carboniferous period. It has likewise shown that, 
during the earlier half of that period, the basin of the Forth was 
dotted over with little volcanic cones, which sometimes threw up 
each its mound of ash or current of lava, and sometimes coalesced 
to form long banks of volcanic ejections, over which the limestones 
and coals were slowly elaborated. The subdivisions of this forma- 
tion adopted by the Survey in the districts yet examined are — 
Coal-measures | 
Millstone grit, or “ Moor rock” 
Carboniferous limestone series. A j 
group of sandstones, shales, and 
coals, with several bands of / 
limestone in the upper part, and 
some thicker beds below J 
Calciferous sandstones 
English Equivalents. 
= Lower part of English Coal- 
measures. 
= Millstone grit. 
= Kocks between the millstone 
grit and the lower lime- 
stone shales. 
= Lower limestone shales. 
I may mention in passing, that Euberslaw, and perhaps some of the 
felspathic hills of that district, seem to mark the site of volcanoes of the time 
