CARBONIFEROUS VOLCANIC ROCKS OF THE FIRTH OF FORTH BASIN. 485 
where by a succession of faults, with a throw in the same direction, the upper 
basalts of Bonnytoun Hill are gradually brought down to the level of the 
sea. 
BONNYTOUN HILL, 
LINLITHCOW 
LOCH. 
STINE. FIRTH OF FORTH, 
x, 
c & 
Fig. 25.—Section from Linlithgow Loch to the Firth of Forth. 
Among the ancient volcanic phenomena of the Basin of the Firth of Forth, 
mention may, in conclusion, be made of the evidence for the former existence 
of thermal springs and saline sublimations or incrustations. Among the tuffs of 
North Berwick a fetid limestone has been quarried, which bears indications of 
having been deposited by springs, probably in connection with the volcanic action 
of the district. The rock has the peculiar carious wavy structure with minute 
mamillated interstices so common among sinters. It contains minute grains of 
iron-bisulphide and flakes of white kaolin, which probably represent decayed 
prisms or tufts of natrolite. The lower limestones of Bathgate furnish abundant 
laminz of silica interleaved with calcareous matter, the whole probably due to 
the action of siliceous and calcareous springs. Some portions of the limestone 
are full of cellular spaces, lined with calcedony.* In a recent communica- 
tion to this Society, I described the discovery of a saline water among the 
volcanic rocks to the west of Linlithgow. A bore was sunk to a depth of 420 
feet without reaching the bottom of these rocks. The water that rose from 
it was found to contain as much as 140 grains of chloride of sodium in the 
gallon. Jt is not improbable, as I have suggested, that this salt was originally 
produced by incrustations on the Carboniferous lavas immediately after their 
eruption, as has happened so often in recent times at Vesuvius, and that it was 
then buried under the succeeding showers of tuff and streams of lava.+ 
* “Geol. Survey Memoirs,” op. cit. p. 49, et seq. 
+ “Proc. Roy. Soc. Edin.” vol. ix. p. 367. 
[Parr II. 
VOL, XXIX. PART I. 61 
