236 
CAVERNCrtJS ROCKS. 
lake of Lucerne. The calcareous beds of the Cuckivano 
and the neighbouring mountains keep pretty regularly the 
direction of N.N.E. and S.S.W. Their inclination is some- 
times north and sometimes south; most commonly they 
seem to take a direction towards the valley of Cuma’nacoa ; 
and it cannot be doubted that the valley has an influence* 
on the inclination of the strata. 
W e had suffered great fatigue, and were quite drenched 
by frequently crossing the torrent, when we reached the 
caverns of the Cuchivano. A wall of rock there rises per- 
pendicularly to the height of eight hundred toises. It is 
seldom that in a zone where the force of vegetation every- 
where conceals the soil and the rocks, we behold a great 
mountain presenting naked strata in a perpendicular section. 
In the middle of this section, and in a position unfortu- 
nately inaccessible to man, two caverns open in the form 
of crevices. "We were assured that they are inhabited by 
nocturnal birds, the same as those we were soon to become 
acquainted with in the Oueva del Guacharo of Caripe. Hear 
these caverns we saw strata of schistose marl, and found, 
with great astonishment, rock-crystals encased in beds of 
alpine limestone. They were hexahedral prisms, terminated 
with pyramids, fourteen lines long and eight thick. The 
crystals, perfectly transparent, were solitary, and often three 
or four toises distant from each other. They were enclosed 
in the calcareous mass, as the quartz crystals of Burgtonna,t 
and the boracite of Lunebourg, are contained in gypsum. 
There was no crevice near, or any vestige of calcareous 
spar.J 
d'Arpenas in Savoy, and in the valley of Estaub^e in the Pyrenees. 
Another transition rock, the grauu-akke of the Germans (very near the 
English kil/as), exhibits the same phenomenon in Scotland. 
* The same observation may apply to the lake of Gemunden in 
Styria, which I visited with 31. von Buch, and which is one of the most 
picturesque situations in Europe. 
f In the duchy of Gotha. 
J This phenomenon reminds us of another equally rare, the quartz 
crystals found by M. Freiesleben in Saxony, near Btirgorner, in the 
county of Mansfeld, in the middle of a rock of porous limestone (rauch- 
wakke), lying immediately on the alpine limestone. The rock crystals, 
which are pretty common in the primitive limestone of Carrara, line the 
insides of cavities in the rocks, without being enveloped by the rock 
itself. 
