Evening star. [volume] (Washington, D.C.) 1854-1972, 1885-06-17
CITY AND DISTRICT.
Protection from I.ixh,utne.
70 the Editor of THE EVENING STAR:


Protection from Lightning.
To the Editor of THE EVENING STAR:
In view of the public interest felt in the pro-
lection of the monument from destruction by
lightning, I conclude that any light thrown
upon the subject will be of interest to your
readers.
In the Nautical Magazine of 1s43 will be
found history of the effects of lightning on
some 200 ships of the English navy, collected
from the logbooks of HI. NJ. ships-a history
which may claim to be considered as a valuable
record of the phenomena of electrical storms.
frigates and IS stoops of war and smaller YES
sells. There were destroyed severely dam
aged in these cases, 164 lower masts and 1872
topmasts. In 1918 nearly one-half OF the in
shore feet under Lord Exmouth, while block
aiding Touion, were on one occasion struck at
the same time by lightning and more or less
disabled. Amer an elaborate Investigation of
this question, both experimentally and by a
corded in the logbooks OF the navy, Sir W;
the prevailing views and opinions relative to
the nature of lightning and the general opera
consider the whole question as based upon far
more practical and general principles than
those commonly entertained. Without stop
ping to consider whether electrical phenomena
were derived from the operation of an invisible
duid or fluids always present to us, and attract
able or attracted by certain kinds of matter, he
came at once TO the immediate results of ex-
perience, and merely assumed in conformity
with these results that what We call lightning
Is an explosive form of action OF some unknown
natural agency when forcing its way through
bodies or other matter, the constitution of
which is such as to resist its progress. For ex-
ample. such matter atmospheric air. or such
bodies as glass pitch, wood and many others,
such as metals and some other bodies, the con-
stitution OF which is favorable to the progress
Of electrical agency, then this explosive form
OF action termed lightning no longer obtains,
but is converted as it were into quiescent cur
rent, the amount of explosive or expansive
force being always in some direct ratio of the
resistance, that the great law which deter
mined tho path of a stroke of lightning and its
attendant destructive effects was really law
dependent upon this general fact that so far
As the unknown principle or agency we term
electricity was concerned every substance is in
respect TO any specific attraction alike indiffer-
emf to it,-a conclusion fully borne out both by
the experiment of Cavendsh and CoulOmb who
found that an electrical charge is independent
ofthe nature of the substance upon which it is
accumulated, and that an equal division of
electricity always obtains without any regard
70 the kind of substance of which bodies con-
Msf;-that in the progress of what is called
stroke of lightning the electrical agency, what
ever it be, seeks to pursue q course which upon
the whole is the least resisting. If metallic
bodies are present and happen to lie in a
position favorable to that course, then they be-
come necessarily subject to the operation of the
discharge; but if not in such position, although
present then the discharge becomes determined
bodiesand hence It IS that the msts of shg
are shfvered in pieces. The whole question is,
therefore, resolved into question of resistance
and distance, and 1t is to the laws deducibIe
from practicable scientific investigation OF
these elements that we must look for an ade-
and caprfcous course of the electrical discharge
as seen in its effects on the monument under
the form ; OF lightning, and in the several anom
lous instances in which it appears to seize upon,
or avoid, good conducting matter.
The French philosophers, under the impress
and that conducting bodies can attract and
oelermlne the course of lightning, We're led to
bndng as defense its APPLIED to
effects In the usual way of lightning-rod
such rod could protect surrounding bodies
within circular distance equal to twice the
radius of its elevation Isee Annales dc Chime
ct de Physique, volume 26l which is by no
means general truth. Experience is at
variance with such deduction. For ex-
ample, In the cases of ships in the British navy,
isisRc and a. damaged by iight1ins we find
main mast. An this, in fact. depends on the
or that direction, and hence lightning does not
always strike the highest point or fall in a GER
ing deductions bearing on this question, and
derived from an analysis OF the numerous
instances above alluded to, are not without
IT appears that In regard to Ships lightning
strikes upon the top-gallant masts or highest
In five times it strikes the topmasts. or next
highest points. In about one in seven 1t strikes
the lower masts. and in about one in fifty
stroke of lightning must frequently assaiI q
ship In directions more or less obiique In two
ming on the main mast only; in about one i in
nve cases on the foremost only in about one in
twenty on the mizen mast only; In about one in
eighty instances on the jibboOm; in about one
instance In. 200 lightning has struck the ex-
tremity Of yard arm without falling on the
masts. The fore and main masts may be struck
simultaneously, or the main and mizen masts
and even all three masts simultaneously: but
m a N1YS1x
elusive Of the main mast.
-, We further find that once in sixteen instances
stream, producing a sort of double or even
treble discharge in about one in twenty cases
s as, mas ts Ialem o6auey In respect Of the
foremost has been struck, a chain conductor
having been applied to the main mast
These important deductions from large col
lection OF facts evidently confirm the view Just
taken OF discharges Of lightning and prove that
specific attractive power resident i'm metallic
bodies, attached to the masts and yards or
otherwise forming portion of the hull but by
other causes foreign as it were to the mere pres
ence of such bodies, and which are to be con-
sidered rather as the patients than the agents
ming.
Admitting then the truth of these examples
1t should follow that if ship or building were
ofelectrical discharge no damage could nossi
bly, occur to 1t by lightning, since at the instant
ofthe electrical discharge striking upon any
point Of the general structure, the ifgftning
would Immediately vanish, and would be con.
verted into what may be considered as a COM
paratively quiescent current or currents of cleo
tricity, having unlimited room for expansion
In all directions. To arrive. therefore, at per
feet security for ships and buildings in electro
cal storms, We should endeavor TO bring the
general fabric into that passive or non-resisting
stare ~ would assume supposing the whole
structure were metallic throughout or nearly so
as possible.
The closer we approximate to such condi-
ton the greater the security
n. Fl. VAN ZANDr
Washington, June 10Th, 1888.
Rrof. Henry Upon Lightning Rod
Points.
To the Editor Of THE EVENING SrAR