8 SIXTH REPORT — 1836. 



a thermal spring having the temperature of 90° in this country, 

 ought to stand higher in the scale than one of 100'' in Mexico, 

 and a spring at 70° might justly be termed thermal in the one 

 latitude, but not in the other. 



It is on this principle that I have constructed a table, which 

 will appear at the close of this Report, conceiving, that although 

 the exact mean temperature of the locality can in many instances 

 be only guessed at, and in the majority must not be regarded as 

 fully determined, still no error need arise from my mode of ex- 

 pression, as the ascertained temperature of each spring may be 

 readily computed, by simply adding the number which gives the 

 assumed mean temperature of the spot, to that indicating the 

 excess of heat inferi-ed to belong to the spring itself. 



Now Prof. Bischof of Bonn* has remarked, that in almost 

 every case the temperature of mineral springs (amongst which 

 we of course do not include land springs, or waters derived from 

 a superficial source,) is such, as places them, according to the 

 definition just given, amongst thermal ones ; and indeed the 

 mere circumstance of a difference in this respect existing among 

 them is in itself a strong presumption that such is the case ; for 

 it is evident that, except where a spring has its origin in certain 

 high mountains adjoining, the coldest of the series will approach 

 nearest to the mean temperature of the locality, whilst the re- 

 maining ones must derive their excess of warmth from some in- 

 dependent cause. 



Tluis Bischof examined about twenty springs near the Lake 

 of Laach, and found the temperature of the coldest of them to 

 exceed that of the place by nearly 2 j degrees of Fahrenheit. 



This rule held good even amongst the springs of countries 

 like Hessia, Hanover, Bavaria, and Wurtemberg, where no such 

 decided indications of recent volcanic action exist. 



The same remark applies likewise to Artesian wells. Thus 

 the temperature of forty-eight springs bored in and near Vienna, 

 was found by observations made in November 1820, to fall be- 

 tween 52°'25 and 57°*2, whereas the mean temperature of Vi- 

 enna is only 50°"80. 



It would be important, if such observations were followed up 

 in other portions of the globe, as well as within the comparatively 

 limited range to which Prof. Bischof's statements apply. In 

 some countries, for instance, where volcanic action has once been 

 rife, as in the Hebrides and in various parts of Scotland and Ire- 

 land, one might expect some excess of temperature in the springs 

 of the district over the mean of the climate ; whilst in others, 



• Edinhurgh New Philosophical Journal, April, 1836. It is to be regretted, 

 that a translation of the latter portion of this valuable paper has not yet been 

 publislu'd ill the above Joiiniaj. 



