326 CONNECTION OF THERMAL SPRINGS IN VIRGINIA 



Other parts of the Continent, are of this denomination. Out of 

 twenty mineral springs in the vicinity of the Lacher See, which 

 he continued to observe at different seasons for several years, the 

 coldest always exceeded the mean of the place by about two 

 degrees and twenty-five minutes, thus proving them aU to be 

 unquestionably thermal. Similar observations on the springs of 

 the Dippe, Jordan, Pader, and Heder, flowing from the foot of the 

 chalk rocks of llie Teutoburges-wald, brought to light the fact, that 

 out of sixty-six running fresh-water springs, only three had a 

 temperature below forty-seven degi-ees seventy-five minutes, the 

 mean of the place, making sixty-three to belong to the thermal 

 class. In like manner Prof. Forbes found the temperature of a 

 number of copious springs upon the Rhine, not before supposed 

 to be thermal, to exceed by several degi-ees the mean of the place. 



Observations of these slightly thermal^ as well as of warmer 

 springs, though thus numerous in some parts of Europe, have 

 perhaps been too much confined to such regions as are known or 

 may be supposed to have been at one time the theatre of local 

 volcanic activity, to admit of our infemng, with confidence, that 

 the elevation of temperature thus oliserved, is the result of a gen- 

 erally pervasive heat within the earth. Indeed, the very frequent 

 occurrence of intrusive igneous masses, among the rocks of a 

 large part of Europe, is calculated to weaken the force of such an 

 inference generally, as applied to that portion of the earth's crust. 



In this country, the vast belt of mountains occupied by the 

 Appalachian strata, presents, as I conceive, a region peculiarly 

 favorable for nnamhignous observations of this class, in conse- 

 quence of the absence, excepting along its eastern border, of 

 trappean or other erupted rocks. It is therefore greatly to be re- 

 gretted, tliat so little has been done towards an accm-ate determi- 

 nation of the temperature of the perennial springs of this region, 

 more particularly of such as are situated near conspicuous axes 

 and lines of fault. From my own observations made from time 

 to time during the last eight years, chiefly in Virginia, I am led 

 to conclude that a great proportion of the copious and constant 

 springs of this belt, and more especially those of our gi*eat lime- 

 stone valley, are truly though slightly thermal, and that they owe 



