Natural History of Volcanos and Earthquakes. 67 



and Ems, 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 volcanic cone, will probably give exit to a thermal spring, if 

 the borer reach the surface of a stratum or a 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 boritig 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 pres- 

 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 Hoffmannf has pointed out, in the north- 

 west of Gei^many, 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, 

 in every direction. He has given to these valleys the name of 



* A joint-stock company is also at this moment employed in boring into clay- 

 slate rock at Thai- Ehrenbreitstein, near Coblentz, in order to procure thermal 

 springs. Since this spot lies scarcely two German miles distant from the well- 

 known hot springs of the temperature of 75° to 131° F. at Ems, and at a lowe-r 

 level, and since an acidulous spring already exists there, the possibility of the suc- 

 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 Noggeraths Ausflug nach 

 Boh nen. Bonn. 1838, p. 5. Tiie instance of the salt work of JVauenheim, near 

 Friedberg, where a salt spring of 100° F. with immense disengagement of carbonic 

 acid gas was obtained by boring, proves that success is more likely to attend by 

 boring into secondary formations, where a more frequent alternation of various 

 strata exists. At Hofgeismar , near Cassel, a new thermal spring with copious dis- 

 engagement of carbonic acid gas v/as also obtained by boring, in May, 1834. 



t Foggendorfrs Ann. t. xvii, p. 151. 



