446 Hot Springs, and other Natural Features of the Pyrenees. 



ating temperature, yet he believes that the temperatures of 

 these springs in the interior of the globe have undergone no 

 change. 



Thermal springs, it may be presumed, are caused, like other 

 sources, by water entering the fissures of the earth at a high 

 point, conducted thence by channels in the manner of a syphon, 

 and seeking its issue at a lower level. Their high temperature — 

 it has been maintained by Dr. Bianconi at Bologna — is pro- 

 duced by the friction of the water as it passes through its 

 rocky channel. It may also be supposed to arise from the 

 high temperature of the low strata of the earth into which 

 their channels descend. If either of these suppositions is 

 correct, the power of conducting heat that the rocks possess 

 through which they rise must exercise a considerable influence 

 on their temperature, in consequence of which a diminution of 

 temperature will generally be found to accompany a diminution 

 in the volume of the water. A diminution of temperature 

 will also occur with an increase in the volume of the water, if 

 cold surface water should, by any chance, find its way into the 

 spring. In this way all the fluctuations of temperature and 

 volume so frequently observed may be accounted for, without 

 resorting to hidden agencies in the interior of the globe to 

 explain the variations of these thermal springs. The words 

 of Dr. Scoresby Jackson, with which he concludes his obser- 

 vations, appear to us to merit every attention when he says 

 that, in these springs, "there is, perhaps, in no instance, a 

 permanent change of temperature • but the changes observable 

 upon the earth's surface are due to superficial and evanescent 

 causes — such as external temperature, the infiltration of cold 

 surface water, and the like." With these remarks we willingly 

 leave the subject of the Pyrenean springs for the present in 

 the hands of our readers, convinced that the inquiry in this 

 branch of physical science, equally as in every other, will 

 ultimately be attended with success: 



