Evening star. [volume] (Washington, D.C.) 1854-1972, 1902-07-23
DUST FROM VOLCANOES
COMPARISON OF SOUFRIERE'S,
MONT PELEE's AND KRAKAToA's.
Great Distances Which the Seismic
Powder Travels-Traced by
Brilliant Sunsets.

The dust from the Soufriere eruption is
evidently travelling far. 1t arrived at Bar
bados-about hundred miles to the east
on the following day. and now the current
number of Nature states that 1t has fallen
at other places and great distances. 1t
has been collected on ships out at sea: one
was at a distance of seventy miles south
of Barbados; another $40 miles to the
southeast, and a third no less than $50
miles away, out on the ocean to the east
of Pernambuco.
Sir w. Crookes has received dust from
ship $50 miles to the southeast, and from
Roxborough, in the Island of Grenada
roughly south southeast of ST Vincent
and rather less than 100 miles from that
island 1t has also reached Santa Lucia,
about twenty-siX miles north of ST. Vim
cent, but in this direction 1t must have
Travelled more slowly, for not till from the
10Th to the Goth was the island developed
In light hay mist. the result of volcanic
Dust suspended in the air, traces of which
were found on the foliage. Apparently it
was deposited more freely at night, being
probably brought down by the dew. Evil
IDENTIFY 1t has been chiefly carried over the
quadrants from east to south, though it
was noticed on ship 100 miles west of
Santa Lucia about midnight on May Q.
Sunda Straits Eruption.
The dust shot up during the great explo-
1857, descended at a number of places, the
most distant of which was about 1 100 miles
away. This, however, refers only to ma
terial course enough to be identified-the
very finest dust more than made the cir
cult of the globe. 1t was traced, not by
the fall of the dust itself, but by the mar
HSlousiS beaut1ful sunsets which it produc-
ed while floating like thin smoke haze in the
upper air. Whether similar atmospheric
effects will follow the eruptiops Of the
Soufrlere and Mont Peee-for as their most
violent paroXysms occurred on successive
days they can hardly be separated-remains
10 be seen, but, on the whole they are
hardly to be expected
me minute dust from Krakatoa was
eJected to very great height from the
earth surface The report issued By the
Royal Society states that Dr. Verbeek es-
tlmated the steam cloud with which dust
"oula be mingled to have mounted, in one
OF the earlier eruptions. to a height of
ABOUT seven miles, and during the most
tlolent paroxysms on August 20 and q to
between ten and twelve miles
That, however. did not satisfy tho mo
teorologists who discussed the sunset CLOVIS
and other kindred phenomena: for they
came to the conclusion that the dust haze
10 which these We're due must at first have
been floating not less and perhans moro
than thirty miles from the earth's surface
ms material, however, from Krakatoa was
much lighter than that from either the
Soufriere or Mont Pelee which as Prof
Bonney stated at a meeting of the GeoIooi
cal Society, If very small samples could he
trusted, were almost Identical
Nature of Elected Rock.
The larger masses of rock elected from
the former volcano are rather vesicuIar
lava, of dull gray color slightly speckled
with glass-white felspar; the dust also
when large quantity is together, assumed
much the same tint. The latter consists
OF grams OF scoria and glass with more or
less broken crystals of felspar and two pv-
roXenes. and. like the former represents
variety of the rock called Andesite by
geoloslstS He remarked that the dust
which reached Barbados was comparative
ly speaking. rather coarse-distinctly more
so than that collected by Mr.. E Whymper
on the summit of Chimborazo after a
journey of more than sixty-five miles from
CotopaXi, or than an other far-traveled
dust elected from the same volcano during
that and a previous eruption. 1t was also
coarser than that which reached Barbados
from the Soufrere in 1912.
The effect OF long journey is to sort out
the larger and the heavier particles; for
instance, that from the Soufriere collected at
sea $50 miles to the southeast of the Sou
friere was not only smaller, but also con-
tanned fewer heavy minerals than that from
Barbados. A similar sorting process oc-
Cured in the krakatoa eruption. There.
as Prof. Judd describes in the report of
the Royal Society, the chemical composition
of the dust at the greatest distance was
very nearly identical with that Of the al
most colorless CLASSY punice which was
collected as it floated on the sea. This how
ever, was from the first, bulk for bulk
rather lighter than the Soufriere rock,
and the shape of its flakes perhaps better
adapted for floating. that the powder
from these recent eruptons does not seem
likely to travel far as that from kra-
katoa.