HYPOTHESIS OE “ELEVATION CRATERS.” 497 
the truncation on a grand scale of some large cones in Java 
and elsewhere.* 
Among the objections which may be considered as fatal to 
Von Buch’s doctrine of upheaval in these cases, I may state 
that a series of volcanic formations extending over an area 
six or seven miles in its shortest diameter, as in Palma, could 
not be accumulated in the form of lavas, tulFs, and volcanic 
breccias or agglomerates without producing a mountain as 
lofty as that which they now constitute. But assuming that 
they were first horizontal, and then lifted up by a force act¬ 
ing most powerfully in the centre and tilting the beds on all 
sides, a central crater having been formed by explosion or 
by a cliasm opening in the middle, where the continuity of 
the rocks was interrupted, we should have a right to expect 
that the chief ravines or valleys would open tow’ards the 
central cavity, instead of which the rim of the great crater 
in Palma and other similar ancient volcanoes is entire for 
more than three parts of the whole circumference. 
If dikes are seen in the precipices surrounding such craters 
or central cavities, they certainly imply rents which were 
filled up with liquid matter. But none of the dislocations 
producing such rents can have belonged to the supposed pe¬ 
riod of terminal and paroxysmal upheaval, for had a great 
central crater been already formed before they originated, or 
at the time when they took place, the melted matter, instead 
of filling the narrow vents, would have flowed down into the 
bottom of the cavity, and would have obliterated it to a cer¬ 
tain extent. Making due allowance for the quantity of mat¬ 
ter removed by subaerial denudation in volcanic mountains 
of high antiquity, and for the grand explosions which are 
knowm to have caused truncation in active volcanoes, there 
is no reason for calling in the violent hypothesis of elevation 
craters to explain the structure of such mountains as Ten- 
eriflfe, the Grand Canary, Palma, or those of central France, 
Etna, or Vesuvius, all of which I have examined. With re¬ 
gard to Etna, I have shown, from observations made by me 
in 1857, that modern lavas, several of them of known date, 
have formed continuous beds of compact stone even on slopes 
of 15, 36, and 38 degrees, and, in the case of the lava of 1852, 
more than 40 degrees. The thickness of these tabular layers 
varies from 1-^ foot to 26 feet. And their planes of stratifi¬ 
cation are parallel to those of the overlying and underlying 
scoriae which form part of the same currents.f 
Nomenclature of Trappean Rocks. — When geologists first 
began to examine attentively the structure of the northern 
* Principles, vol. ii., pp. 56 and 145. 
t Memoir on Mount Etna, Phil. 'Frans., 1858. 
