River Falls journal. [volume] (River Falls, Pierce County, Wis.) 1872-2019, 1904-07-07
WHAT LIGHTNING CAN DO.
When 1t Strikes Tree the Heat Gen.
crates Steam from the Sap.


The explosive force of lightning acting
on dead wood is not, as a rule, so great
as when living trees are struck, though
Sir William Harris shows that 1.-The
masts of ships OF the line, three feet in
diameter and ITO feet long, bound with
hoops of iron half an inch thick and five
inches wide, the whole weighing about
eighteen tons, have been in many in
stances torn asunder and the hoops Of
iron scattered about the decks" 1t viii
be found, as q rule, that trees are struck
by lightning far more often than are
| buildings, even II the trees and the build
lngs are close together This is partly
because the trees are as a rule higher.
But there must probably be some I'M
known reason, not only for the frequency
| with which trees are struck, but for the
recurrence OF such shocks in the case
| or particular trees, or trees in the same
locality. The commonest form Of injury
IS that the current passes down the bark
| OF the tree, stripping off n band, wider
or narrower, from top to bottom. Some
times on an oak two or three OF these
lightning marks are seen, evidently
caused at different times
There must be something in the form
or situation or earth" below the trees
which endangers 1t. An instance is
| quoted in Mr.. Anderson's interesting
book of the Church of ST. Mary, In
| Genoa, which was frequently struck by
| lightning, sometimes as often as twice a
| year. 1t was noticed that the electric
force always followed the same track. 1t
was discovered later that the walls were
clamped with iron, and that the lightning
| had followed the patch In which the
metal offered the greatest continuity, de-
stroying the zone between.
ii the ground below the tree or build
| ing is hard and dry, the contact with
| the earth, in which the lightning expands
! IFS force md dsnapcaS iS 5talo,,1f ona
the destruction of the object struck Is
/ likely to result. This may explain the
| frequency with which a BLASTED" tree
is seen extending its dead arms on the
summit Of some rocky cliff or peak. The
| ground below IL is dry, and does not
easily lead away the current into the
| earth.
! At the same time, thunder clouds I'M
| doubtedly tend to discharge, or perhaps
| 1t would be safer to say that the trans
| mission from the cloud to the earth more
| frequently takes place, near pieces Of
| water and along the course of rivers than
| elsewhere
In park in one of the eastern coun-
! ties there is a large lake. The park con-
tains more trees struck by lightning than
the whole of the rest of the estate. Some
miles away is a road, called locally the
! lightning road from the frequency
! with which accidents have occurred
there, either to trees, horses, cattle or
| passengers. In this park there recently
| occurred an instance of the explosive
| effect in certain circumstances not per-
fectly known.
| A very tall spruce, probably 100 feet
| high, was exploded" from top to bot
| tim into pieces the size of the wood used
| in making chairs. Every shred OF bark
was stripped from them, and the wood
| looked as If it had been shredded up for
| firing A similar instance occurred some
| years ago, when an oak in the grove be-
mond park, exploded under lightning
shock. The bark flew off and simply
disappeared in small patches, and the
rest of the tree was shattered into white
| fragments.
In these cases it is proha Die that the
| current sets up such a tremendous heat
| that all the sap in the tree is converted
| into superheated steam, which explodes.
| The greater the heat, the more OF the
| cells in which moisture lies are exploded.
and the greater the destruction Of the It's
| sues Of the tree. AS there Is most mois-
ture between the bark and the trunk,
the first and greatest explosion takes
| place there, instantly driving the bark
away into space Frequently the explo-
| sion only takes place at that point.
AS Sir Hiram Maxim pointed out after
| the great explosion of Mont Pelee, q very
| similar method is now used by the Amer
| lean manufactures of wood pulp. The
| logs of fir are placed in a strong cham
| Der, and there subjected to the action of
| superheated steam until the water in
| every cell is converted into explosive gas.
| The chamber Is then opened, and the log
explodes, converting itself into wood
| powder.-London Spectator.