* 
Natural History of Volcanos and Earthquakes. 65 
of the clefts in the whole clay-slate rocks so that the gas will be 
evolved wherever these clefts are open at the surface. If these 
fissures open above the bottom of the valley, and therefore are 
| not filled with water, at least not up to the opening, then the gas 
= will escape from them with a hissing noise. If, on the other 
hand, they open from beneath the bottom of the valley, and are 
3 therefore filled with water, then the gas will escape bubbling 
; | through the water, and present entirely the appearance of a min- 
3 eral spring. If, lastly, these fissures be covered by alluvium, 
3 which, hevertheless, does not form an air-tight covering, then 
the gas will escape silently from the ground, and such places are 
recognized from the seanty vegetation which exists there. I 
= know but one of the first description of fissures in that district, 
2 which is found close to the first mineral spring, called Fehlenbor, 
in the valley of Burgbrohl, between Ténnisstcin and Burgbrohl. 
uch a fissure is also found in the Lifel, in the Brudeldreis, as it 
is called, not far from Biresborn. Fissures filled with water, 
from which gas is evolved, are tolerably numerous, as, for exam- 
ple in the valley of Burgbrohl. I formerly considered these 
Spots (which are~constantly met with in the vicinity of the - 
brooks, and consist of little basins filled with water) to be actual 
mineral springs. If, however, the basin be emptied out, or the 
Water drained off, it is at once perceived that no water springs up, 
but that merely an escape of gas takes place. I have had an op- 
Portunity of causing such gas-springs to be enclosed, and found 
e disengagement of carbonic acid gas to be extremely copious.* 
F issures, covered by accumulated earth, are very frequently met 
With. If such a place presents a slight excavation, in which the 
888 collects, suffocated animals, as birds, mice, frogs, &c., are 
Commonly found in it. 
As Springs run in the most different directions between the 
Surfaces of strata, and through the fissures of the strata, so also 
do these disengaged gases. I have often had occasion to cause 
©Xcavations to be made, in places where a scanty vegetation 
rendered the disengagement of carbonic acid gas at some depth 
Probable. Fissures were often met with in the trass, out of which 
rose abundant streams of this gas. Sometimes natural canals 
€ trass were found under a covering of Spharosiderit, which 
Fe lta ig ci 
cere der Chemie et Phys. t. lvi, p. 129. 1829.) 
ol, xxiv, No. 1.—July, 1839, bis. 9 
