The Washington times., 1901-09-15
sKYsCRAPERs ARE SAFE.
The Tall Office Buildings No
Damaged by Lightning.

Without doubt lightning was the first
electrical phenomenon that was ever OBJ
served by human beings. To this day 1t
remains the least known and least un-
derstcod of natural electrical manifesto
tions. except, perhaps. TIE aurora.
There is a vast deal Of popular miscon-
ception concerning the danger of light
ming and the nature of 1t. The lightning
flash is discharge from a cloud at
high potential with reference to the earth
When the atmosphere Is charged with
water. vapor and some eddy or current
in its colder upper strata is DETECTED
downward, causing condensation and
exceedingly minute drops of water are
formed, each bearing an electrical charge.
The consolidation OF these into larger
drops results in a very great increment
of the potential of the charge. since the
capacity of the drop varies with its di-
ameter and the volume of the drop with
the cube Of the diameter.
The consequence OF this is that it takes,
for example, eight drops consolidated to
make one of twice the diameter of the
constituent drops. and the charge on the
surface of the consolidated drop will be
four times as great as that upon the sur
face of its elements. In this way. as the
small water particles unite to form drops
which fall rain. the potential of the
charge they carry Increases until it at
tains enormous values and the lightning
flash leaps to the earth. which may be re-
garded simply as a body of very great
electrostatic capacity. This discharge,
which is called lightning, is apt to be
more or less destructive. although the en-
ergy of an individual flash is perhaps not
very great
Often the conditions are such that the
discharge takes on an oscillating charac-
ter, producing violent surgings of cur
rent. No very accurate measurements
have been made upon the current invoIv-
ed, but it is taken to be of the order of
1000 to 5000 amperes.
The electrO-motive force necessary to
cause a flash mile long is probable seve-
raj million volts, and. of course, the power
of the flash measured in watts is very
great, but its duration is ccrrespondingly
short.
Protection of property and life from
lightning flashes has been subject that
has entranced the attention of natural
philosophers since Franklin sent up his
historic kite. The net result of more
than century of attempt to secure pro-
lection has been the lightning rod in its
more or less inefficient forms, and the
discovery that buildings OF modern con-
struction, having metallic roofs and often
metallic frames as well, are practically
immune from attack by lightning. The
total number of deaths due to lightning
in any given summer is comparatively
very small-in the ratio Of about one to
each 10000 population in the United
States.
In cities the destructive influence Of
lightning is exceedingly small, although
occasional fires are caused by 1t. especi-
ally where gas pipes abound
Protection of electric circuits from
lightning has been an interesting subject
for research for number of years, and
several highly efficient devices have been
constructed for this purpose.
Today lightning is little feared by the
station superintendent. and should be
very little feared by anyone. The time
honored rule that it is wisest to keep in
the open and not seek the shelter OF trees
is one which common prudence dictates.
Recourse to the feather bed of our an
cestors, however, is no longer ne necessary.
except to quiet the timcrous persons,
handling steel instruments and sitting in
draushts may be utterly dsregarded A
modern building in a city is as nearly
lightning proof and those in it
are as nearly absolutely protected from
lightning as is possible.-Electrical Re
view