GEOLOGY. 269 



It is also recorded that the hot springs at Bagneres de Bigorre, in 

 the same mountain-chain, became suddenly cold during a great earth- 

 quake which, iu 1 (>(!(), 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 

 or " faulted." Similar dislocations in the solid crust of the earth are 

 generally supposed to have determined the spots where active and ex- 

 tinct volcanoes have burst forth; for several of these often affect a 

 linear arrangement, their position seeming to have been determined 

 bv nvat lines of lissure. Another connecting link between the vol- 



V VJ t^ 



eauo and the hot spring is recognizable in the great abundance of hot 

 springs in regions where volcanic eruptions still occur from time to 

 time. It is also in the same districts that the waters occasionally at- 

 tain the boiling temperature, while some of the associated stufas 

 emit steam considerably above the boiling point. But in proportion 

 as we recede from the great centers of igneous activity, we find the 

 thermal waters decreasing in frequency and in their average heat, 

 while at the same time they are most conspicuous in those territories 

 where, as in Central France or the Eifel in Germany, there are cones 

 and craters still so perfect in their form, and streams of lava bearing 

 such a relation to the depth and shape of the existing valleys as to 

 indicate that the eternal fires have become dormant in comparatively 

 recent times. If there be exceptions to this rule,, it is where hot 

 springs are met with in parts of the Alps and Pyrenees which have 

 been violently convulsed by modern earthquakes. 



To pursue still further our comparison between the hot spring and 

 the volcano, we may regard the water of the spring as representing 

 those vast clouds of aqueous vapor which are copiously evolved for 

 days, sometimes for weeks, in succession, from craters during an 

 eruption. But we shall perhaps be asked whether, when we contrast 

 the work done by the two agents in question, there is not a marked 

 failure of analogy in one respect, namely, a want, in the case of the 

 hot spring, of power to raise from great depths in the earth volumin- 

 ous masses of solid matter corresponding to the heaps of scoria and 

 streams of lava which the volcano pours out on the surface. To one 

 who urges such an objection, it may be said that the quantity of solid 

 as well as gaseous matter transferred by springs from the interior of 

 the earth to its surface, is far more considerable than is commonly 

 imagined. The thermal waters of Bath are far from being conspicu- 

 ous among European hot springs for the quantity of mineral matter 

 contained in them in proportion to the water which acts as a solvent ; 

 yet Prof. Ramsay has calculated that if the sulphates of lime and of 

 soda, and the chlorides of sodium and magnesium, and the other min- 

 eral ingredients which they contain, were solidified, they would form 

 in one year a square column nine feet in diameter, and no less than 

 140 feet in hight. All this matter is now quietly conveyed by a stream 

 of limpid water, in an invisible form, to the Avon, and by the Avon 

 to the sea ; but if, instead of being thus removed, it were deposited 

 around the orifice of eruption, like the silicious layers which encrust 

 the circular basin of an Icelandic geyser, we should soon see a con- 

 siderable cone built up, with a crater in the middle ; and if the action 



