President's Address. 
117 
small streams disappeared and afterwards burst out afresh 
during the shock from an earthquake, forming springs 
whose temperature in 1803 was 158° Fahr. It is worthy of 
remark that in 1832 Mr Bullock found the heat of these 
springs to be only a little above the temperature of the 
climate. The hottest springs in South America were found 
by Humboldt to contain the smallest amount of mineral 
matters in solution. Their temperature, however, would 
appear to be less constant than those of Europe, with a 
temperature ranging from 122° to 165° Fahr., which have 
undergone no change during the present century — -that is 
to say, since the application of scientific research by means 
of the thermometer and by chemical analysis ; whereas 
Humboldt found those of Las Trincheras to increase 12° 
in twenty-three years. Hot springs, then, show that a 
heating cause does exist deep in the earth's crust ; and 
their wide distribution tends to prove the wide distribution 
of that cause, whatever it may be. 
V. The Increase of Temperature in Mines in proportion 
to their Depths and in the Water flowing from Borings made 
for Artesian Wells. — This argument is of modern date, and 
has a much higher scientific value than any of the others. 
It seems to have originated with Gensanne, who first 
applied the thermometer to this investigation, and ascer- 
tained the important fact that the temperature really in- 
creases with the depth. His experiments began in 1740, 
and were carried on in the lead mines of Giromagny, 
near Befort, to a depth of 1420 feet. Subsequent observa- 
tions were made by Saussure in the deserted galleries 
of an excavation which had been made at the salt-works 
of Bex, in Switzerland. Humboldt and Freiesleben made 
numerous experiments in 1791, in the Freiberg mines ; 
and the former observer, during his travels in South America, 
experimented on the temperature of mines to the depth of 
1713 feet. Similar observations were made in Saxony by 
Daubuisson and Trebra, and in the lead and silver mines of 
Brittany ; and in our own country by Messrs Bald, Dunn, 
and Fen wick, in the coal mines of the north of England, 
