New-York tribune., 1891-08-27
pROTECTION 1GILYST LTGHTNIYG.

Professor II. \. Rowland, in The Baltimore Sun.
Recent scientific study has swept away some OF tho
sdercd the best for protection OF buildings is to provide
a metal roof, with ample number Of metal conduc-
tors leading 10 the ground which will receive and carry
OF the electric bolts from the clouds Copper IS the
best material but Tin or iron viii answer the purpose
always suggest the placing Of the conductors at
the corner Of a building, so that all parts will be
equally protected.
the purpose equally well. The physical laboratory
of the Johns Hopkins University IS protected from
lightning by the roof and spoutlng You can safely
class all patented lightning rods rs being Of little value
beyond conducting rods that any man can put up him
SELF because the simple pincipe underlying all Is
that the lightning will follow the best conductor Tic
idea largely adopted in the erection Of lightning rods
that small band OF glass VIII prevent the electric
current from passing to better adjacent conductor
seems playful While it is true that lightning is at
Tacted 10 an elevated point or angle when YOU cast
ycur eyes over city Ike Baltimore and sec the large
number of such points and angles the of pointed
rods fades into insigniGcance compared with the
illustrated by the incident Of lightning striking the
great monument in Washington several years ago.
The monument IS capped with a piece Of aluminium,
which has metal c connection with the ground by means
Of tie iron work OF the interior, but the lightning did
not strike the top Of tic cap 1t descended TO some
distance from the apex burst a portion Of the stone
and, running along the copper into the interior
leaped without any metallic connection to the
iron framework, and passed TO the ground
angles and crossing the sides Of the immense cap
recommended by me at nat time for tho future pro
lection Of the monument and has probably been con-
struCtcd. The ground connection to be through
the internal irOnwOrk spoken Of. Somewhat similar
these methods is that OF the Peabody Library. The
iron shelving connected with the metallic roof ana
resting a stone foundation which might be shattered
BY stroke Of lightning has been connected with tho
ground by metal conductors, and no danger from
lightning + apprehendd d.
Lightning has liked portion Of a building 10
strike. The stroke may fall at the centre Of the ROOF
and while 10 runs along the surface Of n body. the
| body may he broken or crushed by the enormous
pressure brought b. bear upon IL, In the same manner
That explosion Of dynamite nitro gycernc would
cause a fracture. / have some fragments OF a church
sprc struck by lightning. which bound together IN
their former relative positions, but exhibiting all the
fractures produced bv the cOncussOn Their is vast
difference between the quantity OF electricity and what
Is known a electrical pressure THIS is illustrated u
| a simple manner by the compression Of The air. n
small quantity OF air can be compressed to the same
| degree 81 obtain great expansive force rs "A
large quantity. The quantity OF electricity I'm "a stroke
| 4 lightning Is not nearly as much as masses along
almost any electric wire the street but the voltage
electric pressure Of the street Wirc l. rarely 5000!
volt is the basis on which the pressure Is estimated
The voltage Of the lightning stroke Is roughly estl-
mated at O.OOO,OOOOOO volts In addition 10 this ap,
pallng difference, II may he said that the cnrrcnt uI
the wire l. constant and continuing while the lightning
dart IS delivered In the one tIOhundrcfth part OF
second auch an astounding force IS capable Of dolhs
| many strange things.
In speaking II places Of safety during an electrical
Storm Dr. Rowland said that probably safe piaoo
any other would be iron bedstead, provided le &
ground connection Is perfect, this being In line VIII. wiz,
the above theory that tic lightning would follow to
best conductor. .