594 
PROFESSOR FORBES ON THE TEMPERATURES 
VII. Caudiac. 
A. Geological Position. — These trifling springs are merely noticed on account of 
their geological position, which is in a limestone country, but characterized by the 
intrusion of small patches of granite, as at Bagneres. They occur in the magnificent 
valley of the Aure (the upper part of which is one of the most peculiar and least fre- 
quented scenes in the Pyrenees), a little above Arreau. 
B. Specialties of the Springs. — C. Temperature. — There are several springs ; they 
are sulphureous. They have but little warmth, and are not abundant. A mean 
bathing establishment exists. 
VIII. Bagneres de Luchon. 
A. Geological Position. — The springs of Bagneres de Luchon issue from granite 
very near its junction with clay slate. This portion of granite is not marked in 
Charpentier’s map, though it forms part of a regular band crossing the valley at and 
above Bagneres de Luchon, and is, I have every reason to believe, connected to the 
eastward with the granite of the valley d’Aran in Spain, and to the westward pro- 
bably with that of Oo. Its mineralogical character is generally less crystalline than 
that of Oo ; but I am confirmed in my opinion of its identity by having found near 
the Lac d’Espingo granite in situ, containing beautiful arborescent mica, similar to 
the mica palmier found in granite masses near Luchon, and which have every ap- 
pearance of belonging to its immediate vicinity. 
B. Specialties of the Springs. — It is a curious fact that all the chief springs of 
Bagneres de Luchon issue from the granite within a few feet of one another, although 
their properties are believed to differ considerably, and their temperatures certainly 
do. They are kept separate by partitions connected with a vertical wall, injto which 
slabs of stone (which may be removed) are cemented. The springs are called La 
Reine, La Grotte Superieure, La Source aux Yeux, La Blanche, and La Froide ; but 
all of these, excepting the two first, are apt to mix with one another ; and I even 
learned that such a mixture was practised in order to give a greater apparent supply 
to some of the more esteemed of the springs. It is quite certain too that rain water 
mixes with some of these, which with other facts immediately to be noticed, render 
observations of temperature here of little avail. My observations were made on the 
springs as they flowed from beneath the wall just mentioned. These springs are 
highly sulphureous, and the two whose temperature I measured were copious. 
C. Temperature. — Height of Bagneres de Luchon, 2008 feet (Charpentier). 
The springs of Luchon have undergone most surprising changes. Camperdon, a 
writer of credit, and himself physician for thirty years at this place, assures us that 
the Source de la Reine was cold until 1755, when (on occasion of the great earthquake 
of Lisbon) it assumed a temperature of 41° Reaumur. The hot springs of many parts 
