10 SIXTH REPORT — 1836. 



perature of thcrjr.al springs is often inconstant. Thus in Vene- 

 zuela, Boussiiigault and Rivero* found the waters of Mariana 

 64° Cent., whereas Humboldt a few 3ears before determined it 

 to be 59° ; and that of Funcheras 92"°-2, which Humboldt had 

 found to be 90- °4 Cent. 



But in the interval between these two observations had oc- 

 curred the great earthquake, which overwhelmed the Caraccas 

 and other towns situated in the western Cordilleras. 



The same explanation however cannot be extended to those 

 thermal springs which are unconnected with volcanic action, and 

 concerning these the testimony is of rather a conflicting nature. 

 Thus Angladaf has compared the temperature often springs in 

 the Pyrenees as ascertained by him in 1819, with that determined 

 by Carrere sixty-five years before, and in all of them found a di- 

 minution, amounting in one instance to 27°, but in the rest va- 

 rying from half a degree to 7° of Fahrenheit. The same ob- 

 server found an abatement of 2° in the spring of Molitg in the 

 eastern Pyrenees after an interval of only two jears. 



On the other hand, it id remarkable that Berzeliust in 1822 

 found the spring of Carlsbad to possess the identical temperature 

 which belonged to it in 1770, according to the observations of 

 Becher, viz. 164° Fahrenheit. Yet so contradictory is the evi- 

 dence, that this very spring is reported by Klaprotli, at a period 

 intermediate between the above two observations, as being 8° of 

 temperature lower. 



With regard indeed to thermal springs in general, it must, I 

 believe, be admitted, that no observations have been yet made 

 with thermometers of sufficient exactness to set the question at 

 rest) and I therefore conceive, that a valuable legacy has been 

 bequeathed to science by Prof. Forbes in the report on the tem- 

 perature of the thermal springs of the Pyrenees and others, which 

 he has lately laid before the Royal Society of London, were it 

 only for the pains he had previously taken in verifying, and in 

 comparing with an uniform standard, the instruments he em- 

 ployed. 



In the absence, hoAvever, of direct experiments, we may be 

 authorized on general grounds to presume, that the temperature 

 of thermal springs, in countries not exposed to present volcanic 

 operations, undergoes no sensible change during a long period 

 of time. 



If any change did take place, it would probably be from a 

 higher to a lower degree, rather than the reverse; and as several 

 of the thermal springs which were knovvu and resorted to by the 



* Aiinales de Chimie, 1. xxiii. p. 274. 



+ Mhnoires sur les Eaux Mineralcs, 1S27, p. 65. 



i Aiinahs de Chimin, t. xxviii. 



