383 



same ; and as a more likely occurrence, even were we to suppose that 

 no uniform secular diminution took place, that it would be liable to 

 occasional irregular fluctuations. The influence of earthquakes on 

 the temperature of hot springs is also admitted ; and it would be very 

 desirable to learn, from a series of consecutive observations, whether 

 abrupt changes, similar to those which have occasionally been noticed, 

 are not of frequent occurrence. 



The author has diligently laboured to collect, by observations made 

 on the spot, materials for supplying this great chasm in the natural 

 history of our globe. As an essential preliminary means of obtaining 

 accurate results, he applied himself to the verification of the scales of 

 the thermometers he employed in these researches : and he describes, 

 in a separate section of this paper, the methods which he adopted 

 for the attainment of this object. He first fixed with great precision 

 the standard points of each thermometer, namely the freezing and 

 boiling temperatures of water, by a mode which he specifies : and 

 afterwards determined the intermediate points of the scale by a me- 

 thod, similar to that of Bessel j namely, that of causing a detached 

 column of mercury to traverse the tube j but simpler in practice. 

 Instead of employing for that purpose columns of mercury of arbi- 

 trary length, and deducing by a complex and tentative process the 

 portions of the tube having equal capacities, the author detaches a 

 column of mercury from the rest, of such a length as may be nearly 

 an aliquot part of the length of the scale for 180° 3 and causes this 

 column to step along the tubej the lower part of the column being 

 brought successively to the exact points which the upper extremity 

 had previously occupied : so that, at last, if its length has been pro- 

 perly chosen, the upper end of the column is found to coincide with 

 the end of the scale : and this being accomplished, it is easy to apply 

 to every part of the actual scale of the instrument the proper correc- 

 tions, which may, for greater practical convenience, be drawn up in 

 the form of a table. 



In the next section, the author gives a detailed account of his ob- 

 servations of the mineral springs of the Pyrenees, made during the 

 months of July and August, 1835, following them in their natural 

 order from west to east, and describing their geological positions, 

 the special circumstances of interest relating to them, and their 

 actual temperatures. 



In the third and last section he extends his inquiries to the hot 

 springs met with in some other parts of Europe ; and in particular, 

 those of the baths of Mont d'Or and of Bourboule, in France ; of 

 Baden-Baden, in Germany; of Loesche, or Leuk, in the Vallais ; of 

 Pfeffers, in the canton of St. Gall, in Switzerland ; and the baths of 

 Nero, near Naples. The final results of all the observations con- 

 tained in this paper are presented in the form of a table, with com- 

 parative columns of those derived from some unpublished observa- 

 tions of M. Arago, and of those of M. Anglada. 



