tered the river about three miles above the town of Aderno, and not
only occupied its channel for some distance, but, crossing to the
opposite side of the valley, accumulated there in a rocky mass.
Gemmellaro gives the year 1603 as the date of the eruption.[281] The
appearance of the current clearly proves, that it is one of the most
modern of those of Etna; for it has not been covered or crossed by
subsequent streams or ejections, and the olives which had been planted
on its surface were all of small size, when I examined the spot in 1828,
yet they were older than the natural wood on the same lava. In the
course, therefore, of about two centuries, the Simeto has eroded a
passage from fifty to several hundred feet wide, and in some parts from
forty to fifty feet deep.

The portion of lava cut through is in no part porous or scoriaceous, but
consists of a compact homogeneous mass of hard blue rock, somewhat
inferior in weight to ordinary basalt, and containing crystals of
olivine and glassy felspar. The general declivity of this part of the
bed of the Simeto is not considerable; but, in consequence of the
unequal waste of the lava, two water-falls occur at Passo Manzanelli,
each about six feet in height. Here the chasm (B, fig. 16) is about
forty feet deep, and only fifty broad.

The sand and pebbles in the river-bed consist chiefly of a brown
quartzose sandstone, derived from the upper country; but the materials
of the volcanic rock itself must have greatly assisted the attrition.
This river, like the Caltabiano on the eastern side of Etna, has not yet
cut down to the ancient bed of which it was dispossessed, and of which
the probable position is indicated in the annexed diagram (C, fig. 16).

On entering the narrow ravine where the water foams down the two
cataracts, we are entirely shut out from all view of the surrounding
country; and a geologist who is accustomed to associate the
characteristic features of the landscape with the relative age of
certain rocks, can scarcely dissuade himself from the belief that he is
contemplating a scene in some rocky gorge of a primary district. The
external forms of the hard blue lava are as massive as any of the most
ancient trap-rocks of Scotland. The solid surface is in some parts
smoothed and almost polished by attrition, and covered in others with a
white lichen, which imparts to it an air of extreme antiquity, so as
greatly to heighten the delusion. But the moment we reasce