The heavy clouds of ashes which were thrown out on this occasion
gathered in the early morning into a mighty shadow over Naples and the
neighborhood; the sun rose pale and obscure, and a long, dim twilight
reigned afterward.
Such were the phenomena on the western side of Vesuvius. They were
matched by others on the eastern aspect, not visible at Naples, except
by reflection of their light in the atmosphere. The lava on this side
flowed eastward, along a route often traversed by lava, by the broken
crest of the Cognolo and the valley of Sorienta. The extreme length to
which this current reached was not less than an Italian mile. The cubic
content was estimated to be half that already assigned to the western
currents. Taken together they amounted to 20,744,445 cubic metres, or
2,804,440 cubic fathoms; the constitution of the lava being the same in
each, both springing from one deep-seated reservoir of fluid rock.
The eruption of lava ceased on the 16th, and then followed heavy
discharges of ashes, violent shocks of earthquakes, thunder and
lightning in the columns of vapors and ashes, and finally heavy rains,
lasting till the 3d of July. The barometer during all the eruption was
steady.
Breislak made an approximate calculation of the quantity of ashes which
fell on Vesuvius during this great eruption, and states the result as
equal to what would cover a circular area 6 kilometres (about 3 1/2
English miles) in radius, and 39 centimetres (about 15 inches) in depth.
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