OF CERTAIN HOT-SPRINGS IN THE PYRENEES. 453 



most of the thermal stations in the Pyrenees. The utmost that I have met with 

 in the form of a continuous record is contained in work (Eaux Minerales 

 * des Pyrenees) by Professor Filhol of Toulouse. At page 97 of his book, M. 

 FiLHOL has given a table of observations made at Bagneres-de-Luchon, at irre- 

 gular intervals between 1st August 1849 and 15th April 1853; but during that 

 period there are only eighty-six daj^s of observation. It is to be regretted that, 

 from one so highly respected and so eminently fitted to undertake the task, we 

 have not a longer and more connected series of observations. But, far from 

 charging M. Filhol with lack of zeal, we owe him a large debt of gratitude 

 for the labour which he has bestowed on the subject, and for his very valuable 

 record. The value of the table is enhanced by the facts that the observations 

 are -all made by the same person, exactly at the same points of each spring, 

 with the same instruments, they being verified on several occasions. There- 

 fore, as the observer justly remarks, no doubt can attach to his results. 



From his laborious personal observations, M. Filhol is convinced that the 

 temperature of springs — even those best regulated and most protected from water 

 of infiltration— 25 7iot ahsoluteig inrariahle. With respect to the variability of 

 their temperature, he divides the springs of Bagneres-de-Luchon into two groups. 

 In the first group he places those springs which do not vary more than a few 

 tenths of a degree at the season of snow-melting, when the level of surface water 

 in the galleries is unusually high ; and in the second group those springs whose 

 temperature is more variable, the changes being evidently in relation with the 

 height of the surface water. In the latter group, with a change of temperature, 

 there is generally a corresponding change in the volume of water, a lower tem- 

 perature being observed with an increase in the abundance of water. But this is 

 not uniformly so. The increase in the volume of water of a spring, at the season 

 of snow-melting, is not always due to water of infiltration. Occasionally the 

 volume of water is increased without any diminution of temperature ; more than 

 that, there is sometimes a diminution of temperature with a diminution in the 

 volume of water.* 



M. Filhol believes that springs with a high temperature are less susceptible 

 of variations than those of a low temperature.f 



* A diminution of temperature does not always follow tlie increase of surface water : Dr 

 Garigou, of Ax, says : — " Plusieurs sources sont, en effet, psnetrees par les eaux pluviales ou par 

 I'eau des torrents a I'epoque des fortes crues, et en meme temps que leur volume augmente, on peut 

 suivre I'abaissement de leur temperature et ime diminution dans leur richesse en sulfui'e. Pour deux 

 sources, cependant, j'ai pu, pendant I'hiver, a I'epoque de la fonte des neiges, constater une elevation 

 de temperature bien evidente. Pour I'une de ces sources, celle du Rossignol superieur, la tempera- 

 ture s'est elevee de 0'7 ; et pour la seconde, la source Hardy du Breilh, I'augmentation dans le 

 calorique a ete de 1°." — Etude Chimique ct lledicale des Eaux Sul/ureuses d'Ax. 



f " Je crois avoir remarque que les sources les plus chaudes sont celles qui eprouvent le moins 

 de variations ; c'est ainsi que la source Bayen a oscille, dans I'espace de trois ans, entre 67° 25, et 

 1810."— Op. cit., p. 96. 



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