14 Sir C. Lyell on the Mineral Waters of Bath. 
neath the whole, are occasionally seen tesselated pavements still — 
retaining their bright colors, ove of which, on the site of the 
Mineral-water Hospital, is still carefully preserved, affording us — 
an opportunity of gauging the difference of level of ancient and — 
modern Bat 
years many a stream of lava and shower of ashes, were still 
mountains very much the same as they now are in height and 
dimensions from the earliest times to which we can trace back — 
their existence? Yet although their foundations are tens of — 
thousands of years old, they were laid at an era when the Medi- 
terranean was already inhabited by the same species of marine 
shells as those with which it is now peopled; so that these vol- 
ss 9 must be regarded as things of yesterday in the geological 
calendar. 
Notwithstanding the general persistency in character of min- — 
eral waters and hot springs ever since they were first known to — 
as, we find on inquiry that some few of them, even in historical | 
times, have been subject to great changes. These have hap- — 
pened during earthquakes which have been violent enough to 
disturb the subterranean drainage and alter the shape of the 
fissures up which the waters ascend. Thus, during the great 
earthquake at Lisbon in 1755,‘the temperature of the spring — 
called La Source de la Reine at Bagnéres de Luchon, in the © 
Pyrenees, was suddenly raised as much as 75° F., or changed 
from a cold spring to one of 122° F., a heat which it has since — 
retained, It is also recorded that the hot springs at Bagnéres — 
de Bigorre, in the same mountain-chain, became suddenly cold — 
