552 Royal Society. 
changes which can have occurred in that temperature, during any 
period to which history extends, must be so minute as to be inappre- 
ciable. On the other hand, the theory of internal chemical changes, 
which have been assigned as the origin of volcanos, would suggest it 
as improbable that this temperature has remained constantly the 
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; namely, that of causing a detached 
column of mercury to traverse the tube; 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°; and causes this 
column to step along the tube; 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 Dor and of Bourboule, in France; of 
Baden-Baden, in Germany; of Loésche, 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- 
