PECULIAR VOLCANIC PHENOMENA OF PAL AND CHAMBON. 27 
thousand cases of excavation which most hilly countries exhibit, but of which no 
geological hypothesis has yet given any satisfactory account. In this case, the diffi- 
culty of the explanation is increased by the circumstance, that the excavation has 
occurred since the deposition of a very recent lava, a lava which has itself covered 
the boulders due to a previous denudation. 
T need hardly say one word of M. Burat’s assertion, that the lava of Cham- 
bon is an “ épanchement lateral” from the granite wall of the crater of Pal; in other 
words, that it has issued by a subterranean orifice from the same internal focus. 
Such an explanation would be highly satisfactory were it founded on fact. But 
we have seen that no such orifice exists. Did it exist, it must be at a higher level 
than the highest point of the volcanic accumulations D (fig. 2); but the lava has 
there only a few feet of thickness, and beyond, above, and around it, the bare 
granite is everywhere exposed, the circus extending from E to D, being through- 
out entire, generally precipitous, and presenting no fissure. To this may be added 
the fact, that the highest part of D is higher than the present level of the interior 
surface of the crater of Pal, as the following barometrical heights attest. 
Barom. mill. Ht. above Sea. 
1839, June 3.—Lowest part of Crater of Pal, : : : 661°6 3893 feet. 
Highest Boundary of the Crater to NE. (con- 
glomerate), . : : : z 646-9 4537 
Highest point Lava of Chambon, E - 656-1 4134 
The whole relations of this singular formation will, I hope, be made plainer 
by the elevation, or distant perspective view in Plate IV., fig. 3, carefully drawn 
from the top of the Gravenne of Montpezat. The same letters of reference are 
used as far as possible in figs. 2 and 3. 
The crater of Le Pal has acquired some celebrity by the discussions to which 
it has given rise in the Geological Society of France;* having been by some 
regarded as the type of a crater of elevation, as composed entirely of granitic 
strata elevated so as to present a volcano composed of primitive rock. I cannot 
at all partake of this view; and indeed can affirm, from the most careful and re- 
peated examination, that it presents no peculiarity which can cause it to be con- 
sidered as exceptional, unless the insignificant quantity of scorize ejected by it 
(or, at least, which are now visible), which is insufficient to form a true 
cone like that of the neighbouring volcano of Bauzon. The primitive rocks 
appeared to me here as elsewhere to be undisturbed ;—to have no exterior 
configuration whatever, indicating that they have been moulded by the pres- 
sure of lava in the interior ; and certainly not to possess the character of “ in- 
ternal precipices (forming the crater) with gentle external slopes:” the section 
in fig. 2 shews just the reverse. In fact, the granitic eminences by which 
the crater of Pal is partly surrounded, are (as already mentioned) the culmina- 
* Bulletin de la Société Géologique de France. Tom. III, and IV. 
