Hot and Thermal Springs. ' " S7§ 



amounts to 2°.25 in 744 feet on the average. This result can- 

 not be compared with the above, as the temperatures of the air 

 and of the soil were not made at the same places, but at places 

 very different in their climate ; further, because the mean tem- 

 perature at Jltenhergm the years 1830-1832 shewed differences 

 as great as those between that place and Markus Rohl'mg; and 

 lastly, because the observations on the temperature of the soil 

 at Altenherg and Johanngeorgenstadt even shewed an increase 

 of temperature with the height. 



However, these observations seem also to prove that the de- 

 crease of temperature is slower in extensive gradually ascend- 

 ing mountains, but more rapid in steep ones. As there may, 

 therefore, be an infinite number of gradations in the decrease 

 of temperature between mountains which rise almost perpendi- 

 cularly from the surface of the earth, and a gradually ascend- 

 ing inclined plane, all other circumstances being the same ; 

 only such observations can serve for a comparison, as have been 

 made on mountains having a very steep ascent. 



With respect to the decrease of temperature with the height 

 in the frigid zones, we are totally unprovided with observations 

 in those regions, which might serve as data in our calculations. 

 We must, therefore, leave it undecided, whether the relations 

 are the same or different from those which exist in the other 

 zones. If Fourier's hypothesis,* that the temperature of space, 

 or at least of that part of space in which the earth performs its 

 orbit, is about equal to the mean temperature at the poles is 

 correct, no decrease of temperature can be supposed to take 

 place in proportion to the distance from the surface of the 

 earth at the poles. 



We now come to the last means of determining the decrease 

 of temperature with the height, namely, the temperature of 

 springs, which seems indeed to be the simplest method of all. 



In Chapter VI. it has been shewn, that, under the most fa- 

 vourable circumstances, the mean temperature of the soil can 

 only be determined from such springs as have not a constant 

 temperature, because springs of constant temperature always 

 rise out of strata which are situated much lower. But the 



Mem. de I'Inslit. 1824, p. 580. 



