across, darted forth suddenly a thunderbolt which
killed a woman of the name of Bordenave by
burning her bosom without injuring her clothes.
According to the statement of Duhamel du
Monceau, on the 30th of July, 1764, there issued
from a small solitary cloud, in bright sunshine, a
thunderbolt which struck an elm-tree very near
the château Denainvilliers, tearing off a strip of
bark. Bergman saw the lightning dart to a
church steeple from a very small cloud in a very
clear sky. Captain Hossard saw a small cap of
cloud forming around a mountain-top called the
Colombier de Gex, five thousand two hundred
and fifty feet high, which in a few seconds afterwards
sent forth a clap of thunder. These
singular cases require to be explained by further
and more complete observations.

The smoke of volcanoes is often corruscated
by serpentine fires or lone furrows of flames,
resembling zigzag flashes of lightning. These flames
are sometimes accompanied with thunder-claps.
Science may learn something, I submit, by
directing attention to these thunder-storms in
volcanic clouds. Assuming their flashes to be
electric, may they not be similar to the sparks
which issue from the steam of locomotive boilers?

Scarcely less remarkable than the volcanic
lightnings, are the vitrifications from lightning
observable on the rocks of lofty mountains such
as Mont Blanc. But the greatest heights of
thunder-clouds is said to occur above plains.
Fatal thunder-storms have burst forth above
plains, the estimated elevation of which, so high
were they, was not less than twenty-six thousand
feet; and fatal thunder-storms have raged
in valleys the upper surface of which was not
more than ninety-two feet.

Forked or zigzag lightning has been observed
describing the track of a V and of a reversed ?.
Trident or three-pronged lightnings have been
seen within the volcanic dust clouds of Mont
Etna. Kaemtz, the German meteorologist, saw
a flash of lightning split into three forks. A
three-pronged flash of lightning struck at Freiburg
on the 25th of June, 1794: the middle point
struck a house near the cathedral, the southern
prong set fire to a house near a mill in the
suburb, and the northern prong or flash set fire
to a cottage near an adjoining village. The
ancients called fork lightning, when it struck
the ground, the thunderbolt. In sheet lightnings
the clouds seem to rend their black veil
and reveal their inward brightness.

Lightning often resembles balls of fire differing
in size from the size of bullets, to that of
eggs, bombshells, globes, casks, and balloons.

Lightning has been known to strike upwards.
An astonishing instance of this occurrence is
recorded by Arago. Upon the top of Mount
St.Ursula, a lofty mountain in Styria, there is
a church. On the 1st of May, 1700, Jean
Baptiste Werloschnigg, Doctor in Medicine,
and a group of other persons, were standing in
the porch of this church upon the top of the
high mountain. Down the mountain, and half
way towards the bottom of the valley, black
clouds were gathering, and soon they displayed
all the grandeur and terror of a great thunder-storm.
The spectators in the porch of course
deemed themselves quite safe where they were,
the air being serene around them and the sun
shining on them brightly, yet seven of them
were struck down dead. Lightning darted
suddenly up from the upper surface of the cloud,
and killed them by Dr. Werloschnigg's side, on
whose testimony the extraordinary fact is
recorded by M. Arago.

Professor Charles Wheatstone, by curious
calculations and ingenious machines, found out how
to estimate the duration of a flash of lightning.
This is not the place to explain how time can
be calculated to the thousandth part of a second.
But it may be stated here that he ascertained
from his experiments, and competent men
accepted his results, that the most brilliant fork
and the widest sheet lightnings endure less than
the thousandth part of a second of time. But
I have to state a greater wonder still. The
duration of the spark of the electrical machine
is not the millionth part of a second, and yet I
have seen Mr.Talbot produce photographs by
its transient light!

Thunder-clouds occur which are continuously
luminous. The sky at Beziers, says M. Rozier,
on the 15th of August, 1781, became, after
sunset, quite dark, and whilst he was watching
the lightnings, a band appeared about three feet
wide, and stretching an angle of about sixty
degrees. Then, there came another above it
about half the length with a space of equal
length between them. These luminous zones
were nearer the earth than the storm-clouds,
and lasted nearly a quarter of an hour.

Beccaria of Turin records having seen in very
dark winter nights, and during the intervals
between falls of snow, clouds emitting red light
sufficiently bright to enable him to read ordinary
print. The phosphorescence of clouds must
not be confounded with the aurora borealis.
General Sabine, and President of the Royal
Society, when engaged in determining the lines of
magnetic force, remained some time at anchor
in Loch Scavig, in the Isle of Sky. This loch is
surrounded with high mountains of bare rock, one
of which is almost always in a cloud of vapours,
brought by south-westerly winds from the
Atlantic. Streamers ascended from it. But although
they resembled auroras, they proceeded from the
cloud itself, and were not auroras seen through
it. Irish fogs are sometimes phosphorescent.

The "corn-bleck" of the Swedish and Scottish
peasants, is silent lightning which is accused of
blighting barley. There have been many records
made of silent lightning. In some instances the
lightnings flashed for a long time without any
thunder having been heard. Thunder, on the
contrary, has issued from clear, cloudless, and serene
skies, in which no lightning was seen. Volney, to
say nothing of more ancient instances, has
recorded that on the 13th of July, 1788, he heard
at eight and three-fourths geographical miles from
New Orleans four or five thunder-claps, the sky
being without clouds. These thunderings of serene
skies have occurred in countries in which they