CALCAREOUS SPRINGS. 
cent soil, a jointed pipe of wood or metal is intro- 
duced. When a vein of water is struck, it often hap- 
pens that the fluid rushes violently up the tube, and 
plays over the top like a fountain. This is often 
owing to the disengagement of air or carbonic acid 
gas. At Hammersmith, in England, the rush of wa- 
ter from a depth of 3fi0 feet was so great as to in- 
undate several buildings and do considerable dam- 
age ; and in another place, a sufficient stream was 
obtained to turn a wheel, and raise the water to the 
upper surface of the houses. At Tours, in France, 
at the depth of several hundred feet, the water rose 
32 above the level of the soil, and the discharge 
amounted to 300 cubic yards in 24 hours. Excava- 
tions have been made in this manner to a depth of 
1200 feet. 
Mineral and Thermal Springs, — Springs are rarely, 
if ever, quite pure, owing to the solvent property 
of water, which, percolating through the earth, al- 
ways becomes more or less charged with foreign 
matter. Carbonate, sulphate, and muriate of lime, 
muriate of soda, and iron, are frequently present in 
spring-waters. Some are more highly charged with 
these substances than others, and are, accordingly, 
called mineral springs. In these the foreign ingre- 
dients are in a state of chemical solution, and, ac- 
cordingly, so intimately blended with the water as 
not to effect its clearness. The use of such waters 
strongly teaches us the force of habit ; for though 
at first they may be highly nauseous and disagree- 
able, in a short time they lose these properties and 
become pleasant to the taste. 
Warm springs have received the name of ther- 
mal, and they rise up through all kinds of rock, as 
granite, gneiss, limestone, or lava, but are most fre- 
quent in volcanic countries. In many volcanic re- 
gions, as in Italy, jets of steam issue from fissures 
at a temperature high above the boiling point; and 
if such volumes of steam should come in contact 
