Hot and Thermal Springs, 85f 



of temperature and chemical composition during long periods of 

 time. 



The same effects which earthquakes are capable of causing in 

 springs, will also be produced by active volcanos, for volcanic 

 action is always accompanied by earthquakes. Besides, by the 

 rising of the melting lava, the upper strata of the earth become 

 heated, and thus it may happen that springs rising in a volcanic 

 soil, although from an inconsiderable depth, may, as Anglada 

 himself remarks, be warmer than others which do not rise in 

 volcanic districts. 



All such variations may, therefore, take place without injury 

 to the hypothesis, that the superior temperature of the interior 

 of the earth, progressively increasing with the depth, is the prin- 

 cipal cause of the heat of thermal springs. It is, therefore, un- 

 necessary to seek refuge with Anglada in such an improbable 

 subterranean electrical process. 



It still remains to be ascertained whether a gradual alteration 

 of the temperature of springs, in places where there are neither 

 traces of former nor of present volcanic action, and where earth- 

 quakes are not frequently felt, can be conceived possible. With 

 respect to the phenomenon itself, it is difficult to determine whe- 

 ther it exists or not ; for all depends upon the thermometers, 

 which, so constructed as to serve for a comparison of observa- 

 tions on the temperature of springs, have only been in existence 

 for about one century. But it is well known that even until a 

 much later date, exactly corresponding thermometers were con- 

 sidered great rarities ; and it is not long since attention has 

 been drawn to several circumstances, upon which the accuracy 

 of these instruments depends. It is true that considerable dif- 

 ferences of temperature may be observed in springs even with 

 inaccurate thermometers ; but if they proceed by degrees, and 

 are not perceptible until a long period has elapsed, the most 

 perfect apparatus is necessary for their detection. Accord- 

 ins to the observations of Carrcre in 1754, and those of An- 

 glada in 1818 and 1819,* the temperature of ten thermal springs 

 in tlie East Pyrenees, has decreased 1°.125 to 60°. 75 during that 

 period, and the decrease was found to be greater the higher the 

 original temperature of the springs. 



Anglada, p. G3. 



