Hot and Thermal Springs. d6i 



These salt springs prove, therefore, that even thermal ppringa 

 can participate in the variations of the external temperature* 

 The differences between maximum and minimum are found, 

 however, to diminish, as the mean teniperature increases. But 

 for this very reason it is improbable that springs originating in 

 the superficial strata, in which the variations of the external tem- 

 perature are still felt, should shew a constant degree of heat. 

 Springs of constant temperature must, therefore, alwfiys be con* 

 sidered as thermal. The difference between the temperature of 

 the coldest of the constant or nearly constant springs, and the 

 mean temperature of the neighbouring variable springs, is not 

 the same for all places. According to the table, these differences 

 are, for the neighbourhood of Berlin 0°.675; in Sweden hardly 

 2^°; near Burgbrohl, about 2^ miles from Bonn, they rather ex- 

 ceed 4J°, and the warmest of the salt springs of Werl^ which 

 surpasses the probable temperature of the coldest of the neigh* 

 bouring springs by 6°.075, is not yet constant, but shews a year- 

 ly variation of temperature of 4J°. * 



It may be that the extent of these differences of temperature 

 at a certain place, depends, in some measure, on its geographical 

 latitude, as, according to Chap. VIII, the depth to which the 

 external temperature continues to be felt, is greater in higher 

 than in low latitudes, the annual variations of temperature of the 

 air being also greater there than here. But the less considerable 

 these variations are, the less are also the yearly variations of tem- 

 perature of the waters which filter into the earth, and the more 

 easily will they, after a short percolation of the earth's crust, 

 give rise to springs of a constant temperature. Tlie influence 

 of latitude upon the scale of the annual variations of tempera- 

 ture must, however, certainly be very much modified by other 

 circumstances, — namely, the elevation above the surface of the 

 sea at which the springs rise, the fiUering of the atmospheric 

 waters in more or less considerable streams through the earth, 

 and the degree of conductibiliiy of heat of the soil. Tlie extent 



• From a comparison of the observations on the temperature of a sprinj^ in 

 a well sunk in Loudon, which was constant, and indicated sa^.SJfi, with thf 

 mean temperature of that capital, the difierence api^^ars tp be for Xbai lociu 

 \\iy 3°.C to 44° Annales de Chim. et de Th^s., vol. xxi. p. 31C. 



