371 
of Edinburgh, Session 1876 - 77 . 
stalactites of common salt upon the walls and slopes of a volcanic 
crater after eruption, and the appearance of the same substance 
upon the surface or within the chinks of recently-consolidated lava 
streams, have long been observed. On Yesuvius vast quantities of 
salt have been gathered again and again, and have been used by 
the inhabitants at the foot of the mountain. Among the Icelandic 
volcanoes the same fact has occurred. But besides this outward 
and conspicuous manifestation, chemical analysis has revealed the 
presence of chloride of sodium in many volcanic rocks, either 
diffused through their crystalline matrix or entangled within their 
individual constituent minerals. In such volcanic minerals as 
Hauyne, Nosean and Sodalite it has been found to be noticeably 
present. It has been extracted even by pure water from clink- 
stones, basalts, and from various plutonic rocks. 
There can be little doubt that it is to this volcanic origin that 
the large admixture of salt in the Linlithgow water is to be traced. 
The bore may have reached a stratum of ancient lava or tuff, 
originally permeated or incrusted with salt, which may have been 
dissolved by percolating water, and yet have remained in solution 
below for want of any ready means by which the water could 
escape to the surface. This escape is now provided by the bore, and 
the water is consequently now removing the salt from the rock. 
It may be mentioned that some of the best known saline waters 
of Scotland rise from volcanic rocks. At the Bridge of Allan, water 
containing 95 grains of chloride of sodium in the gallon takes its 
rise from near the top of the enormous mass of lavas and tuffs 
erupted during the Lower Old Bed Sandstone period, and forming 
now the chain of the Ochil Hills. At Pitcaithley, Bridge of Earn, 
water containing 114 grains of the same salt in the gallon rises 
from the same volcanic band, while at Dunblane, water with 48 
grains of common salt in the gallon comes through the lower parts 
of the red sandstones of that district, which lie upon the same 
great volcanic series. In most of these cases the rise of the saline 
water appears to have been determined by an accident, such as the 
sinking of a bore for water, or, as at Bridge of Allan, during the 
search for minerals. 
