[ 571 j 
XXVI. On the Temperatures and Geological Relations of certain Hot Springs, par- 
ticularly those of the Pyrenees ; and on the Verification of Thermometers . By 
James D. Forbes, Esq. F.R.S., Professor of Natural Philosophy in the University 
of Edinburgh . 
Received February 17, — Read March 24, 1836. 
If the chemistry of mineral waters has been as yet prosecuted to a very limited 
extent, notwithstanding the number of eminent analysts who have engaged in the 
research, much more has every other topic connected with their origin and nature 
been superficially treated*. The characters of springs of every kind are so important 
as to deserve minute and laborious research ; and notwithstanding the partial essays 
of Von Buck and others, the whole subject remains in a state of confusion, and is 
involved in incongruities and contradictions -f”. The chief point to which the ob- 
servations about to be described were directed, is the temperature of thermal springs ; 
and, referring to this point alone, we might prove the almost total absence of exact 
data on the subject. Every traveller, to be sure, has measured the temperature of 
springs, but few have been aware of the difficulties which even this apparently simple 
inquiry involves. 
We should have considered the accurate determination of the temperatures of 
thermal springs the first step towards a theory of their production The constancy 
of that temperature from day to day, from year to year, from century to century, 
would appear one of the most essential facts to determine ; yet I am aware of scarcely 
a single published observation capable of being satisfactorily employed in such an 
inquiry. Not only are the errors of the instruments unknown, but the circumstances 
* “ Quiconque a serieusement reflechi sur cette matiere, conviendra sans peine avec M. Alibert que la 
science des Eaux Minerales est, pour ainsi dire, a refaire.” — Anglada, Traite des Eaux Minerales du De- 
partement des Pyrenees-Orientales, Pref. 
t I have for a number of years been making collections respecting springs of all kinds, of which the present 
can be considered but as one division. Feeling, however, the doubtfulness of my ever completing this investi- 
gation, and the importance of stating completely all that relates to minute topographical details soon after the 
observations are made, I have lost no time in proceeding to the reduction of these Pyrenean experiments. 
X “ Depuis qu’il est assez generalement convenu que les sources thermales empruntent leur haute tempera- 
ture a la chaleur propre des couches terrestres plus ou moins profondes d’ou elles proviennent, l’etude des 
changements qu’elles peuvent eprouver a acquis une nouvelle importance. II serait sans doute curieux de 
savoir si la cause chimique mineralisatrice de ces eaux dans laquelle on cherchait jadis l’explication de leur 
chaleur extraordinaire augmente d’intensite par le progres du temps, ou si elle s’affaiblit ; mais en tous cas, on 
n’aurait ainsi decouvert qu’un fait local et sans portee ; envisage de l’autre maniere, le phenomene, au con- 
traire, se rattache aux plus grandes questions de la philosophic naturelle.” — Arago. 
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