: * 
Natural History of Volcanos and Earthquakes. 67 
and Hms, which rise in deeply hollowed valleys in clay-slate 
rocks, are thus produced. 
We may also easily conceive the possibility of obtaining a 
thermal spring by boring. A slight glance at the figure will show 
that a hole bored into a clay-slate rock in a valley, in the vicinity 
of a voleanic cone, will probably give exit to a thermal spring, if 
the borer reach the surface of a stratum ora slate surface com- 
municating with the cleft between the volcanic and the clay- 
slate rock. A successful attempt of this kind was actually made 
a few years ago, by boring into the clay-slate rock at the foot of 
the basaltic hill, the Landskrone in the Ahr valley, about three 
German miles north of the Laacher See, when a copious mineral 
was obtained of the temperature of 58° F., affording consider- 
able disengagement of carbonic acid gas. Indications prognosti- 
cating a favorable result of this undertaking were indeed 
ent, inasmuch as a mineral spring already existed at the distance 
of but a few steps from the spot.* 
Phenomena, perfectly resembling those which are observed 
where volcanic masses have actually broken through, present 
themselves very frequently. A cleavage, reaching to great depths, 
may also be a consequence of a preceding elevation and fracture 
of the component strata, without an actual breaking through 
having taken place. These phenomena are found in formations 
of all ages. Thus Hoffmannt has pointed out, in the north- 
West of Germany, some peculiar valleys which, originally per- 
fectly closed, are surrounded on all sides by a precipitous escarp- 
Ment, whose component strata incline from the centre downward, 
Mevery direction. He has given to these valleys the name of 
cn ; 
known hot springs of the temperature of 75° to 131°. F. at Ems, é 
level, and since an acidulous spring already exists there, the poosrbility, of i 
Cess of this undertaking is as little to be despaired of, as a favorable result can be 
Promised. Leop. von Buch’s remarks on this subject in Néggeraths Ausflug nach 
huen. Bonn. 1838, p.5. The instance of the salt work of Nauenheim, near 
