EARTHQUAKES AND VOLCANOES. 
397 
which it was difficult to force the animals., that we were 
compelled to dismount and pursue our journey on foot. 
About half way up the mountain the dikes of lava became 
less frequent, and the ground more firm and open, and, 
although quite precipitous, yet not difficult of ascent. 
This open belt, however, does not extend to the summit, 
and long before we reached it we were again driven upon 
the beds of sharp, rough, and unsteady lava. 
“ Our course now lay through a deep channel formed 
between two vast currents of lava, composed of enormous 
crags, which in 1844 had flowed out from fissures in the 
side of the volcano. We had not proceeded far between 
these walls of rock when we found the scoriae beneath 
our feet so yielding and unsteady that we could scarcely 
retain our foothold. Frequently we slid back three or four 
yards, thus losing in a moment the advance which it had 
cost us great labor to accomplish. Nevertheless, after many 
efforts and through much, exertion, and after having suf¬ 
fered several severe falls, we succeeded in reaching the 
throat of the mountain. Here the lava was solid and the 
scoriae firm ; and though the slope was very steep and dan¬ 
gerous, yet we found it easier to proceed here than over 
the soft and yielding ashes below. 
“ About mid-day we reached the summit proper of the 
mountain and stood on the edge of the great crater, 
which is surrounded by a wall of immense rocks, irregu¬ 
lar in height, and having a circuit of a mile and a half. 
The area within these strange bulwarks is level; but on 
descending, we found with alarm that it was traversed 
in every direction by profound fissures, varying from one 
foot to five yards in width, from which escaped dense 
clouds of sulphurous smoke. About in the centre of this 
