AND GEOLOGICAL RELATIONS OF CERTAIN HOT SPRINGS. 
573 
Continent, would lead us to infer that constancy of temperature is improbable, and 
that even supposing- that there were no uniform diminution from age to age, occa- 
sional irregular fluctuations would be inevitable. The influence of earthquakes upon 
the temperature of hot springs is also admitted ; and it would be very desirable to 
know from continued observations whether abrupt changes are not frequent, similar 
but on a smaller scale to that, for example, which raised the temperature of the 
Source de la Pieine at Bagneres de Luchon by about 75° on the occasion of the 
earthquake of Lisbon in 1755. Most curious effects have likewise occurred on occa- 
sion of earthquakes to many springs L Baron Humboldt did me the honour to 
mention a circumstance perhaps connected with a similar cause. Two springs in 
South America, at a distance from any active volcano, have increased in temperature 
by 4° centigrade since the period of his observations, as determined by M. Boussin- 
gault. 
It is a singular fact that we are not only unacquainted with the progressive varia- 
tions of temperature in springs during long periods of time, but even with the diurnal 
or monthly changes to which many thermal waters are probably subject. The usual 
statement of the constancy of the heat of such springs at all seasons is abundantly 
general, but perfectly vague. I have reason to believe that, except in the case of 
particularly abundant springs, it does not hold true ; but I am unacquainted with 
any systematic experiments on the subject, although I have made many inquiries 
on the subject in almost every place I have visited where the medicinal importance 
of the springs had rendered them objects of attention to physicians or intelligent 
persons generally. Such information as I have been able to collect will be men- 
tioned in alluding to the particular localities : I will only observe, that the abso- 
lute constancy of the temperature of springs is a circumstance in itself impossible, 
owing to the variation of temperature of the uppermost strata through which they 
flow at different seasons. When the flow of water is abundant, this, however, appears 
to be very small, or even quite insensible. 
The observations here recorded must always possess a certain degree of value. I 
lament, however, that my want of information on the points just alluded to prevents 
me from assuming that they are directly applicable to the chief object I had in view, 
— the future determination of secular changes small in amount. We may, however, 
conclude, that before a sufficient time has elapsed to render such comparisons a 
matter of interest, more extended local observations shall have made us acquainted 
with the variations (if any) which the regular change of season produces, and those 
which may be due to the meteorological inequalities of various years. 
I shall have the opportunity of pointing out by specific examples, in the sequel, the 
impossibility of as yet commencing any comparisons of the kind alluded to, owing to 
the unsatisfactory vagueness of published observations ; not less from errors in the 
modes of observing than from imperfect instruments, inadequate descriptions of loca- 
* See Gairdner on Mineral Springs, p. 211. 
