1864.] ADDRESS BY SIR CHARLES LYELL. 391 



mans ; for many of them still retain as great a beat as is tolerable 

 to tbe biinian body, and yet when enjploycd by the ancients they 

 do not seem to have required to be first cooled down by artificial 

 means. This uniformity of temperature, maintained in some places 

 for more than 2000 yeurs. together with the constancy in the vol- 

 ume of the water, which never varies with the seasons, as in ordinary 

 springs, the identity also of the mineral ingredients which, century 

 alter century, are held by each spring in solution, are striking facts, 

 and they tempt us irresistibly to speculate on the deep subterranean 

 sources both of the heat and mineral matter. How long has this 

 uniformity prevailed ? Are the springs really ancient in reference 

 to the earth's history, or, like the course of the present rivers and 

 the actual shape of our hills and valleys, are they only of high an- 

 tiquity when contrasted with the brief space of human annals ? 

 May they not be like Vesuvius and Etna, w^hich, although they 

 have been adding to their flanks, in the course of the last 2000 

 years, many a stream of lava and shower of ashes, were still moun- 

 tains very much the same as they now^arein height and dimensions 

 frcm 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 Mediterranean was already in- 

 habited by the same species of marine shells as those with which 

 it is now peopled ; so that these volcanoes must be regarded as things 

 of yesterday in the geological calendar. 



Notwithstanding the general persistency in character of mineral 

 waters and hot-springs ever since they w^ere first known to us, we 

 find on inquiry that some few of them, even in historical times, 

 have been subject to great changes. These have happened during 

 earthquakes which have been violent enough to disturb the sub- 

 terranean drainnge 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 fSource de la Heine 

 at Bagneres 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 Bagneres de Bigorre, in the same mountain-chain, be- 

 came suddenly cold during a great earthquake which, in 1660, threw 

 down several houses in that town. 



It has been ascertained that the hot-springs of the Pyrenees, the 

 Alps, and many other regions are situated in lines along which the 

 rocks have been rent, and usually where they have been displaced 



